''In Japan it was once customary to give young people about to be married a "pillow book." This was a small volume of wood-block prints, often colored, showing all the details of sexual intercourse. It wasn't just that, as the Chinese say, "one picture is worth ten thousand words." It was also that it spared parents the embarrassment of explaining these intimate matters face-to-face.''
Alan Watts, ''The Book On the Taboo Against Knowing Who You Are''