D O C U M E N T 4 2 8 M A R C H 1 9 2 9 3 8 9 can never clearly recall, but among the Mendelssohn lieder, you played the vocal part with special pleasure, I can still hear: “The sun is already rising over the moun- tains & the wood…”[4]— Through playing music, we became friends, & on several occasions Mama suggested that before playing you have supper with us, eating just as we did, but you took absolutely nothing but fruit and “Guzeli”[5] after playing: earlier you had had a mug of soup & a sausage at Dändiliker’s “Alcohol-free,”[6] & that was always enough for you. Now and then you played Hans Wohlwend’s[7] instrument, which was better than yours, & twice that young man also came along, so then there was a trio do you still remember that? At that time you were already working on your dissertation[8] & promised that when you were granted your doctor’s diploma, you would send me a postcard with a “cock-a-doodle-doo,” & I pledged to send you, as a tangible congratulation, a pair of Moor’s heads like the ones we then had on the table—but the news never arrived, alas! Eventually, I learned that you were continuing your studies in Zurich & Bern, & then I followed your successes, travels, etc., in the newspapers. I understand nothing about your work, but I do know that the results of your research & your concentrated intellectual work has immeasurably benefited the world of scholar- ship, & that through them your name has become immortal! Have you had the patience & indulgence to read this far and think about that time once again? I myself will soon be sixty-four years old and live with Mama, who has begun her ninetieth year of life, a humble but satisfying existence. I am still teaching beginners & coach people who sing in Zurich or take violin lessons, & also do needlework for others. Mama has asked me to give you her friendly greetings and good wishes, and I send you a warm handshake and greetings with my utmost esteem, Marie Barthelts 428. From Paul Ehrenfest Leyden, 12 March 1929 Dear, dear Einstein, May you above all be healthy and happy, and may all those whose happiness is particularly close to your heart be well! And we thank you for what you are to us. Your, P. Ehrenfest