I could go for this one that Herodotus reports:
Just need a supply of silver coins.
Quote: Now the most shameful of the customs of the Babylonians is as follows: every woman of the country must sit down in the precincts of Aphrodite once in her life and have commerce with a man who is a stranger: and many women who do not deign to mingle with the rest, because they are made arrogant by wealth, drive to the temple with pairs of horses in covered carriages, and so take their place, and a large number of attendants follow after them; but the greater number do thus,--in the sacred enclosure of Aphrodite sit great numbers of women with a wreath of cord about their heads; some come and others go; and there are passages in straight lines going between the women in every direction, through which the strangers pass by and make their choice. Here when a woman takes her seat she does not depart again to her house until one of the strangers has thrown a silver coin into her lap and has had commerce with her outside the temple, and after throwing it he must say these words only: "I demand thee in the name of the goddess Mylitta": now Mylitta is the name given by the Assyrians to Aphrodite: and the silver coin may be of any value; whatever it is she will not refuse it, for that is not lawful for her, seeing that this coin is made sacred by the act: and she follows the man who has first thrown and does not reject any: and after that she departs to her house, having acquitted herself of her duty to the goddess, nor will you be able thenceforth to give any gift so great as to win her. So then as many as have attained to beauty and stature are speedily released, but those of them who are unshapely remain there much time, not being able to fulfil the law; for some of them remain even as much as three or four years: and in some parts of Cyprus too there is a custom similar to this.
Just need a supply of silver coins.