Divination from the belly, an ancient method now generally believed to have been ventriloquism, the voice sounding low and hollow, as if issuing from the ground. Eusèbe Salverte, author of Des sciences occultes (1834), put forward this opinion, adding, "The name of Engastrimythes, given by the Greeks to the Pythie (priestesses of Apollo)[,] indicates that they made use of this artifice."
Another method of practicing gastromancy connects it with crystal gazing. At one time vessels of glass, round and full of clear water, were placed before several lighted candles. In this case, a young boy or girl was generally the seer, and the demon was summoned in a low voice by the magician. Replies were then obtained from the magical appearances seen in the illuminated glass vessels.
Salverte, Eusèbe. Des sciences occultes. Paris, 1834.
Waite, Arthur Edward. The Occult Sciences. 1891. Reprint, Se-caucus, N.J.: University Books, 1974.
"Gastromancy." Encyclopedia of Occultism and Parapsychology. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/gastromancy
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