A letter written by Albert Einstein to President Franklin D. Roosevelt warning of the threat of Germany building nuclear weapons, ultimately resulting in the creation of the Manhattan Project, sold for $3.92 million at Christie’s on September 10 afternoon, Report informs referring to Cllct.com.

The letter was sold as part of Christie’s sale of part of the famed collection of the late Microsoft co-founder Paul Allen.

With a listed pre-sale estimate of $4 million to $6 million, the letter is one of two written at the time along with scientist Leo Szilard. The original letter is held at the Roosevelt Presidential Library, while this second, shorter copy was kept by Szilard and eventually sold by his heirs. It ended up in the collection of Malcolm Forbes, from whom Allen purchased the letter for $2.1 million in 2002.

Einstein’s manuscript on the theory of relativity sold for more than $13 million in 2021.

Allen, who died in 2018, was a prolific collector, setting a posthumous record in 2022 when his art collection sold for a combined $1.62 billion.