Guillaume L'Hospital is perhaps most famous for his 1696 book Analyse des infiniment petits pour l'intelligence des lignes courbes (Analysis of the Infinitely Small to Learn about Curved Lines), the first textbook ever on . Today he is remembered mainly through , the rights to which he is rumored to have bought from .

L'Hospital, whose name some sources also spell "L'Hôpital," was the marquis of St. Mesme. He was born in Paris in 1661 to Anne-Alexandre de L'Hospital and Elizabeth Gobelin. As a boy, L'Hospital's mathematical talents were readily apparent. By the time he was 15, he had stunned esteemed academics by solving a problem concerning that had posed.

That success set the stage for a long career of distinguished accomplishments in mathematics, except for a brief interruption during which L'Hospital served as a cavalry officer in the French Army. Due to his serious near-sightedness, however, he was forced to resign...