Depictions of sex and abnormal sex can be traced back through the ages, predating the term "hentai". "Shunga", a Japanese term for erotic art, is thought to have existed in some form since the Heian period. From the 16th to the 19th centuries, "shunga" works were suppressed by "shōguns". A well-known example is "The Dream of the Fisherman's Wife", which depicts a woman being stimulated by two octopuses. "Shunga" production fell with the introduction of pornographic photographs in the late 19th century.