Courtesy of LeonardoDaVinci.net

This cutaway scientific drawing, from around 1492 - 94, is Leonardo's only study of figures having sexual intercourse. As a drawing it has no erotic or romantic overtones, being purely the mechanics of the internal parts of the act, in which Leonardo as a scientist was most interested. Leonardo appears to have thought that the act of coition not only transferred the sperm to the female egg but also transferred, from the spinal cord, the spirit or soul to the future embryo. However, in his notes Leonardo also seems sceptical about this traditional notion.