A rare manuscript by theoretical physicist Albert Einstein goes under the hammer in Paris on Tuesday, with auctioneers aiming for a stratospheric price tag.

The manuscript, containing preparatory work for Einstein’s key achievement the theory of relativity, is estimated at between two and three million euros (2.3−3.4 million), according to Christie’s which is hosting the sale on behalf of the Aguttes auction house.

“This is without a doubt the most valuable Einstein manuscript ever to come to auction,” Christie’s said in a statement.