Holy water

Jamie McCrimmon, a Scottish Highlander from 1746, noted that witches were sprinkled with holy water. (TV: The Moonbase)

Holy water was also supposed to be dangerous to demons. During the 12th century, Henri d'Arrée dipped his sword in a font of holy water at a chapel to prepare for battle against the "forest demons"; when it had no more of an effect than a normal sword-blow, he deduced that the creatures were not demonic as he understood the word, despite being clearly "unnatural". (AUDIO: The Green Man)