Engraving depicting Druids being converted to Christianity. The Druids are shown conducting the ritual of oak and mistletoe. One of their number has climbed an oak tree and has cut some of the mistletoe growing on it. In the background, white bulls are being sacrificed. Pliny the Elder described the ritual, writing that it would cure infertility in animals. This drawing comes from David Smollett's Complete History published in 1758.