Gastromancy is an ancient method of divination that is now speculated to have been ventriloquism. The voice of the seer seemed to come from the ground.
Eusebe Salverte, author of the Des Science Occultes (Paris, 1834), put forth the following opinion: «The name of Engastrimythes, given by the Greeks to the Pythiae (priestesses of Apollo), indicates that they made use of the sacrifice.» This explanation, however, is only partial, but the text of Isaiah, «Thy voice shall die as one who hath a familiar spirit,» is inapplicable in such an argument.
All who are familiar with the phenomena clairvoyance recognize that the voice becomes very low in the consequence of a change in respiration. Such was the behavior of the Pythonesses, although this too could have been the result of ventriloquism; such a phenomena presently occurs among the wizards of Greenland.
.Another method of practicing gastromancy is with crystal glasses, round and filled with clear water, which are placed in front of lighted candles. Also, this method is related to crystal gazing. In this instance, a young boy or girl acts as the seer, and the magician summons the demon. The relies or answers are interpreted by observing the magical appearances that are seen in the illuminated glass vassals. A.G.H.
Source: 9.