The Anatomy of Melancholy

Witelo, in book 10 of his Optics, gives another such example of a close acquaintance who, after going without sleep for three or four nights, saw someone riding beside him along a riverbank and making all the same gestures. When more light appeared, the figure vanished. Hermits and anchorites frequently have such absurd visions and revelations because of much fasting and poor diet. Many are deceived by sleight of hand, as Scot has well shown in his Discovery of Witchcraft, and Cardan in On Subtlety, book 18.

Fumigating substances, perfumes, smoke, compound candles, optical glasses and such natural causes make people look as though dead, or as though they had horses’ heads, bulls’ horns and similar animal forms; or make the room seem full of snakes and adders, dark, light, green, red, of every colour, as you may read in Baptista Porta, Alexis, Albertus and others. Glow-worms, fiery apparitions, meteors and the will-o’-the-wisp, which Pliny, book 2, chapter 37, calls Castor and Pollux, and many such things appear on marshy ground, around churchyards, in damp valleys or where battles have been fought; read their causes in Goclenius, Velcurius, Finkius and others. Such scares are often contrived to frighten children with squibs, rotten wood and so on, or to make people look dead, “larger than usual,” bigger, smaller, fairer or uglier: “to make those standing nearby appear headless, entirely on fire, or in the form of demons, take the hairs of a black dog,” and so on, says Albertus.

And so strange, unfamiliar sights are commonly seen through catoptrics. Who does not know that if light is admitted into a dark room through a single small hole, with paper or glass placed over it, the shining sun will project onto the opposite wall all the objects illuminated by its rays? With concave and cylindrical mirrors we can reflect whatever shapes of people, devils or grotesques we please, as magicians commonly do to trick a gullible spectator in a dark room, and make them seem suspended in the air; when there is nothing but a frightening image, such as Agrippa describes, placed in another room.

Roger Bacon is said to have used this art long ago to make his own image appear to walk in the air, although nothing of the kind appears in his writings on optics. But for the most part, what deceives them is in the brain; although I cannot deny that the devil often deludes them, taking his opportunity to suggest and present unreal objects to melancholy people and those who are ill.

To these you may add the roguish impostures of conjurors, exorcists, mass priests and quacks, of whom Roger Bacon speaks in On the Wonders of Nature and Art, chapter 1. They can imitate the voices of almost all birds and brute beasts, and every human tone and tune, speaking within their throats as though from far away. They make their listeners believe they hear spirits, leaving them astonished and terrified. There are also artificial devices for overhearing their confessions, like the whispering place at Gloucester here in England, or the duke’s place at Mantua in Italy, where a concave wall reflects sound. Blancanus explains and mathematically demonstrates the cause in his Echometria.