The History of the Human Heart, or The Adventures of a Young Gentleman was published anonymously in 1759, the same year as John Cleland's Memoirs of a Woman of Pleasure (Fanny Hill), and is another high point in 18th Century erotica. It is set in the same milieu of seduction and brothels, it is however written from a male point of view. The protagonist Camillo, like many young men, is led by his penis, and being from a wealthy family, has the means to go where it leads him. He is not a wicked person, but he is headstrong, impulsive and thoughtless, and he undergoes sexual adventures and misadventures which are variously hilarious and horrifying.
It is not at all as well-known as Cleland's work; in fact the only recent reference seems to be by John Fowles, who in his novel The French Lieutenant's Woman, quoted a passage verbatim as a description of Edward's visit to a brothel, introducing it as follows:
Such scenes as that which followed have probably changed less in the course of history than those of any other human activity; what was done before Charles that night was done in the same way before Heliogabalus--and no doubt before Agamemnon as well; and is done today in countless Soho dives. What particularly pleases me about the unchangingness of this ancient and time-honoured form of entertainment is that it allows one to borrow from someone else's imagination. I was nosing recently round the best kind of secondhand bookseller's--a careless one. Set quietly under "Medicine," between an Introduction to Hepatology and a Diseases of the Bronchial System, was the even duller title The History of the Human Heart. It is in fact the very far from dull history of a lively human penis. It was originally published in 1749, the same year as Cleland's masterpiece in the genre, Fanny Hill.
There follows the description of the introduction of Camillo to the Posture Girl in Chapter V.