Nobel prize-winning physicist Albert Einstein thought about more than just the theory of relativity or gravitational waves. In fact, a letter he wrote in 1954, in which he discussed his inner-most thoughts about God and religion, just sold for $2,892,500.

The letter, estimated to fetch between $1 and $1.5 million, surpassed expectations at Tuesday's auction at Christie's in New York. The "remarkably candid, private letter was written a year before Einstein's death and remains the most fully articulated expression of his religious and philosophical views," according to a statement about the letter on Christie's website.