Albert Einstein's documents revealed on his 140th birthday

There are four personal letters between Einstein and his friend Michele Besso and a letter to his son Hans Albert, who lived with Einstein's estranged wife in Switzerland.

"The German armament must be extremely dangerous," he wrote to his son in 1935, worrying about the rise of Nazi Germany and the war that was brewing.

Einstein himself moved from Germany to the United States in 1933 after the rise of Adolf Hitler.

Present at the event was Karen Cortell Reisman whose father was Einstein's cousin. For her wedding, she recalled, she asked her parents to give her a letter the world-renowned scientist once wrote together with them.

"I didn't really want a piece of china or silver; just this letter," she told the audience in Jerusalem.

"The only thing I inherited from Albert Einstein is his hair texture, the frizzy hair," Reisman said laughingly. "I cannot explain to you the theory of relativity."

The documents were revealed just days before Einstein's 140th birthday. They will be digitized and accessible to the public in the near future. For Gutfreund and his excited colleagues, it was a reason to celebrate.

"I cannot think of a better, more lavish or fitting birthday gift than this," Gutfreund said.