The Kama Sutra is an ancient Earth book on human sexual behavior.
In 2373, while boarding a transport that was about to depart Deep Space 9 for Jupiter Station, Lewis Zimmerman asked a female passenger if she had ever heard of it. (DS9: "Doctor Bashir, I Presume")
Background
According to an interview with Chase Masterson (Leeta), who is good friends with Robert Picardo (Zimmerman), Zimmerman did not have a line in the script once Leeta and Rom finally got together. Picardo ad-libbed, asking a nearby woman, "Excuse me, have you heard of my work on Star Trek: Voyager?" Though Masterson thought the line was hilarious and should have been aired, the line was changed to have him say, "Excuse me, have you heard of the ancient text known as the Kama Sutra?" The reasons for the change are unclear, although Trekkies' notorious reputation for tracking such "continuity" errors may be to blame.