Consider this series of drawings from an old alchemy text. They are one of several such series.
You may also view them here, where you can click on each image to enlarge it a bit.
These images seem to record a mystery that is often also referred to as the sacred marriage, "hierosgamos" or "conjunction of opposites." Are they strictly symbolic of some non-physical union, or do they point to the need for actual union of the sexes as part of a spiritual ritual? Can you learn anything about this mystery?