Ars Amatoria
Sexual manuals have existed since antiquity, such as Ovid's "Ars Amatoria", the "Kama Sutra" of Vatsyayana, the "Ananga Ranga" and "The Perfumed Garden for the Soul's Recreation". ("Prostitution in the City of Paris"), an early 1830s study on 3,558 registered prostitutes in Paris, published by Alexander Jean Baptiste Parent-Duchatelet (and published in 1837, a year after he died), has been called the first work of modern sex research.