As to why I was curious upon a question like this : given that ancient Hinduism has given world the popular literature work of kama sutra, so surely there must be some reference as to a thing like this in our religion, moreover this occupation/practice is as old as any other ancient puja or culture, so surely there must be a piece of script regarding this topic.
what I exactly seek to know : Are there any specific piece of literature discussing about this very topic ? Was this taboo practice considered a sin and why so ? Were there any instances where gods were directly involved in any such thing ?
N.B. : I don't wish to offend anyone.