Scribbled note in the margins of his copy of Diophantus's Arithmetica. He did not live to provide the promised proof, and the conjecture became famous as Fermat's Last Theorem. In 1993 Andrew Wiles, a British mathematician, claimed to have discovered the proof.
Alexander Hamilton, John Church Hamilton (1850). “The Works of Alexander Hamilton: Miscellanies, 1774-1789: A full vindication; The farmer refuted; Quebec bill; Resolutions in Congress; Letters from Phocion; New-York Legislature, etc”, p.43