In the spring of 1863, two paintings of nude women divided Paris — and only one of them made an emperor fall in love. At the official Paris Salon, Alexandre Cabanel's The Birth of Venus stopped visitors in their tracks: a goddess reclining on a bed of sea-foam, luminous and weightless. Napoleon III liked it so much that he bought it on the spot for his own private collection. Today the painting is one of the most visited works at the Musée d'Orsay — and one of the clearest examples of how 19th-century France decided which nudity was art, and which was scandal.