My father is a well-known guitarist and for all of my life, he was on tour several months of the year. When I was a little girl (and even a not-so-little girl), I would treasure each and every postcard I got from wherever it was he’d traveled. And a letter? Well, a full-on letter – written on a sheet of hotel stationery and sent in an ultrathin airmail envelope – was an extra special treat!

Letters from presidents to their political fellows, from famous lovers to one another, from authors to publishers, and letters from soldiers to their parents are always a source of fascination – but there’s a certain gravitas in letters from parents to their children. Here are a few of my favorites:

From Theoretical Physicist Albert Einstein to his daughter Lieserl

"When I proposed the theory of relativity, very few understood me, and what I will reveal now to transmit to mankind will also collide with the misunderstanding and prejudice in the world.

"I ask you to guard the letters as long as necessary, years, decades, until society is advanced enough to accept what I will explain below.

"There is an extremely powerful force that, so far, science has not found a formal explanation to. It is a force that includes and governs all others, and is even behind any phenomenon operating in the universe and has not yet been identified by us. This universal force is LOVE.

"When scientists looked for a unified theory of the universe they forgot the most powerful unseen force. Love is Light that enlightens those who give and receive it. Love is gravity, because it makes some people feel attracted to others. Love is power, because it multiplies the best we have, and allows humanity not to be extinguished in their blind selfishness. Love unfolds and reveals. For love we live and die. Love is God and God is Love.

There is an extremely powerful force that, so far, science has not found a formal explanation to. It is a force that includes and governs all others, and is even behind any phenomenon operating in the universe and has not yet been identified by us. This universal force is LOVE.

"This force explains everything and gives meaning to life. This is the variable that we have ignored for too long, maybe because we are afraid of love because it is the only energy in the universe that man has not learned to drive at will.

"To give visibility to love, I made a simple substitution in my most famous equation. If instead of E = mc2, we accept that the energy to heal the world can be obtained through love multiplied by the speed of light squared, we arrive at the conclusion that love is the most powerful force there is, because it has no limits.

"After the failure of humanity in the use and control of the other forces of the universe that have turned against us, it is urgent that we nourish ourselves with another kind of energy… If we want our species to survive, if we are to find meaning in life, if we want to save the world and every sentient being that inhabits it, love is the one and only answer.

"Perhaps we are not yet ready to make a bomb of love, a device powerful enough to entirely destroy the hate, selfishness, and greed that devastate the planet. However, each individual carries within them a small but powerful generator of love whose energy is waiting to be released.

"When we learn to give and receive this universal energy, dear Lieserl, we will have affirmed that love conquers all, is able to transcend everything and anything, because love is the quintessence of life.

"I deeply regret not having been able to express what is in my heart, which has quietly beaten for you all my life. Maybe it's too late to apologize, but as time is relative, I need to tell you that I love you and thanks to you I have reached the ultimate answer!

"Your father, Albert Einstein"

From actor Jason Biggs to his son, Sid

“I wanted to write you a note on our progress as a father/son team now that you're four months old. I, for one, am having a blast. Judging by your chuckles and coos and general inability to control your bowels when I'm around, I'd say you're having fun too.

“But I want to prepare you for a time when things won't be as easy between us. You see, your daddy—despite his very best efforts—will make mistakes. It is just one of life's many inevitabilities. Now, I know what you're thinking: impossible! Not my daddy! He's so strong and handsome and funny… And handsome! Well, sure. But your daddy is also human. And being that he is a first-time parent, he is learning as he goes. (First thing he should probably learn: stop speaking in the third person.)

“These mistakes will be subtle or obvious. You will shrug them off or you may never forget them. Perhaps, like my father when I was small, I will lose you on a crowded beach, leaving you to wander for what seems like days. You'll have just resigned yourself to becoming one of those weird old dudes who scavenges the beach with a metal detector when you'll be grabbed by a lifeguard who will hold you up, Lion King–style, shouting, ‘Has anyone lost this kid?!’ And I'll come running, shouting back, ‘Yes! Yes! He's mine!’

“I can't predict how I will mess up. But I assure you that everything I do, every decision I make, will be filled with love. And if you are ever unhappy with me, I encourage you to let me know, so that I may make the necessary changes.

“I leave you with an apology, for my future missteps: sorry, kiddo. I promise to do better next time.

“Love always, Daddy

“P.S. I'm also sorry for using the word inevitabilities. I imagine you're gonna have to look that one up.”

From author John Steinbeck to his son, Thom

“Dear Thom:

“We had your letter this morning. I will answer it from my point of view and of course Elaine will from hers.

"First — if you are in love — that’s a good thing — that’s about the best thing that can happen to anyone. Don’t let anyone make it small or light to you.

"Second — there are several kinds of love. One is a selfish, mean, grasping, egotistical thing which uses love for self-importance. This is the ugly and crippling kind. The other is an outpouring of everything good in you — of kindness and consideration and respect — not only the social respect of manners but the greater respect which is recognition of another person as unique and valuable. The first kind can make you sick and small and weak but the second can release in you strength, and courage and goodness and even wisdom you didn’t know you had.

"You say this is not puppy love. If you feel so deeply — of course it isn’t puppy love.

"But I don’t think you were asking me what you feel. You know better than anyone. What you wanted me to help you with is what to do about it — and that I can tell you.

"Glory in it for one thing and be very glad and grateful for it.

"The object of love is the best and most beautiful. Try to live up to it. If you love someone — there is no possible harm in saying so — only you must remember that some people are very shy and sometimes the saying must take that shyness into consideration.

The object of love is the best and most beautiful. Try to live up to it.

"Girls have a way of knowing or feeling what you feel, but they usually like to hear it also. It sometimes happens that what you feel is not returned for one reason or another — but that does not make your feeling less valuable and good.

"Lastly, I know your feeling because I have it and I’m glad you have it.

"We will be glad to meet Susan. She will be very welcome. But Elaine will make all such arrangements because that is her province and she will be very glad to. She knows about love too and maybe she can give you more help than I can.

"And don’t worry about losing. If it is right, it happens — the main thing is not to hurry. Nothing good gets away.

"Love, Fa"

From Clothing Designer Tina Knowles Lawson to her daughters, Beyoncé, Solange, Kelly and Angie

“When I was asked to write an open letter to you, I thought about the hundreds of texts and emails that I have sent to you on holidays and on Sundays, when I ask you to say a prayer to thank God for each other. Every day, I wake up thinking about how much I love, admire, and cherish each of you.

“I gave birth to two of you, but I have four incredible daughters. Writing this brought to mind all the ways you guys have been such a blessing to me.

“When I’m feeling sad or not-so-cute or maybe a little sorry for myself, and you all include me in your group chat and tell me how hot I still look or how cool I am. Maybe you send me a crazy YouTube video. What actually works best is a cute photo of my grandchildren.

“I remember slumber parties after my divorce, when we watched old movies and ate a lot of ice cream. I felt so loved and supported. The roles were reversed, and it was ME who needed nurturing.

“I remember my first date when every one of you weighed in on what I should wear.

“The obvious things about all of you are apparent. You are all strong, beautiful, intelligent, and smart businesswomen. You are so much more than that. You are all kind, generous, and you treat people well. You are all amazing mothers, wives, daughters, sisters, and friends. All of you have total self-respect.

“Beyoncé, I wish people could see how you are when you’re not in front of the camera or on the stage. How compassionate and kind you are to people, how you look them right in the eye when you speak to them. How hard you work, how generous you are with your time and money. How you don’t care if anyone knows about it because you do it from the heart. I wish they could see you with the Make-A-Wish Foundation kids, how patient you are and how your love has helped to extend lives. Yes, you are a huge star, but you have somehow managed to stay grounded and humble in the wake of all your success.

“Solange, I knew when you were born three days late that you would walk to the beat of your own drum. You were always my rebel warrior! Always defending the underdog and fighting for what you believe in. I remember you, at 10 years old, started a petition to remove a bad teacher, and your dad and I were so proud of you. I love that you do not let others define who you are, or what you are. Whether in your music, fashion, or your life, you truly are your own incredible, unapologetic person! As tough as you are, you will drop everything to take care of someone you love.

“Kelly, I know without a doubt that you were a true gift from God. You came to live with us when you were only 11 years old. You were the sweetest, most kind person I had ever met and you still are. You are also a true survivor. You never give up. Your discipline and drive always inspires me. You make me want to take better care of my body and constantly motivate me to exercise and take time for myself. You have the best listening skills and are a loyal friend to many. I’ve seen you take the jewelry off of your arm and give it to someone because you wanted to make them feel good.

“Angie, you are my niece, but we have always been more like mother and daughter! You were always so mature, always challenging me, and questioning why. (Fortunately I never believed in the ‘Because I said so’ or ‘I’m the adult’ crap, either.) I always trusted that you would look out for and protect Solange, Kelly, and Beyoncé, and you did! You still do sometimes. You are so smart and perceptive, and you see through bullshit right away! You’ve always had our backs. Our own family fixer!! You know I call you Olivia Pope!!!!!

“I’m often asked, what was my most proud moment? I would have to say it was at my recent wedding, when all four of you said in your own words that I taught by example and that I helped to make you the women you are today!!!! That was truly my proudest moment!

“All my love, Mom”

If you were to write a letter to your child, what would you tell them? Share your thoughts with us in the comments below!

Sources: Time magazine, Hebrew University, and Steinbeck: A Life in Letters (book).
Cover image: Bokic Bojan / Shutterstock.com