Kama Sutra, explicit and matter-of-fact treatment of the erotic arts and sexual intercourse.

Pleasures should not be sought for, because they are obstacles to the practice of Dharma and Artha, which are both superior to them, and are also disliked by meritorious persons.... This objection cannot be sustained, for pleasures, being as necessary for the existence and well being of the body as food, are consequently equally required. They are, moreover, the results of Dharma and Artha. Pleasures are, therefore, to be followed with moderation and caution. No one refrains from cooking food because there are beggars to ask for it, or from sowing seed because there are deer to destroy the corn when it is grown up. Thus a man practising Dharma, Artha and Kama enjoys happiness both in this world and in the world to come. The good perform those actions in which there is no fear as to what is to result from them in the next world, and in which there is no danger to their welfare.

— from the Kama Sutra, by Vatsyayana

Vatsyayana (2nd–3rd century AD) was a Hindu philosopher and attributed author of the Kama Sutra, a practical guide to everyday matters most famous for its explicit and matter-of-fact treatment of the erotic arts and sexual intercourse.