First Posted: May 22, 2021 02:52 AM EDT Photo : John Moore/Getty Images Three times more than its expected selling price, an Albert Einstein handwritten letter with his world-changing E=mc2 equation has been sold at an auction house based in Boston for more than $1.2 million on Friday. Individuals responsible in the archives of the Einstein Papers Project at the California Institute of Technology and the Hebrew University of Jerusalem noted that aside from the one sold at Boston, there are only three other known examples of Albert Einstein's written equation. According to RR Auction, the auction house where the most recent purchase happened, this fourth example of Albert Einstein handwritten letter with an equation is the only one in the hands of a private collector and only recently made its public appearance. In the initial assessment of the auction house, they had expected it to sell for around $400,000.