The 20-centimeter glass phallus, dating from the 16th or 17th century, was discovered in a two-meter-deep latrine shaft connected to the living quarters of a noblewomen's religious house in Herford.

With minimal ingenuity, any historical period can be made to dissolve into the ones around it. Take the rock revolution—that great shift which, emerging in the mid-nineteen-fifties and established by ...