Atlas Obscura points to the Karpeles museum. This is Einstein's manuscript of the theory of relativity. You'll also find samples  From William Harvey, Galileo, Christopher Columbus, John Locke, and Rene Descartes

"I thought of that while riding my bicycle". Albert Einstein pic.twitter.com/CuTFmgUoqC

— ✍ Bibliophilia (@Libroantiguo) February 27, 2015

Albert Einstein at Lincoln University, Pennsylvania, May 1946. pic.twitter.com/VYBNjGpirk

— ✍ Bibliophilia (@Libroantiguo) February 10, 2015

Albert Einstein & Niels Bohr in Belgium, 1930 Photo by Paul Ehrenfest pic.twitter.com/INQ3fqaKET

— History In Pictures (@HistoryInPics) January 19, 2015

Albert Einstein (pictured here in fluffy slippers) was asked to be the president of Israel, which he declined. pic.twitter.com/s9qdjtADZ7

— History In Facts (@HistoryInFacts) January 17, 2015