A postcard from Albert Einstein’s trip to what is now Israel just fetched $56,000 at auction.

The card in question comes from February 1923, when the Jewish genius traveled to British Mandate Palestine. While in the Middle East, Einstein sent the postcard to Zionist leader Arthur Ruppin.

“To my dear Mr. Ruppin,” Einstein wrote, “we are having unforgettable days in Palestine. With the sun shining, in cheerful company. Your wife is standing next to me and looking at what I am writing about her. She is counting the days until you come back.”

Einstein’s note is below a message from Ruppin’s wife, Hanna, who wrote, “Dear Arthur, a pleasant tour of the city. Included is a picture by Prof. Einstein.”

Indeed, on the reverse side there is a self portrait done by Einstein, above an image of a ship.

The rare postcard sold through RR Auction, and was purchased by an anonymous source out of Boston for $56,250.

“This is an extreme rarity, and although Einstein was known to accomplish drawings, signed self-portraits are virtually inaccessible,” said Bobby Livingston, executive vice president at RR Auction.

Einstein was famous for his support of Jewish causes and Israel. He was even offered the post of president of the Jewish state, which he politely declined.