Among the ancient superstitions of Spain, were those of the existence of profound caverns in which the magic arts were taught, either by the devil in person, or some sage devoted to his service. One of the most famous of these caves was at Salamanca. Don Francisco de Torreblanca makes mention of it in the first book of his work on magic, C. 2, No. 4. The devil was said to play the part of Oracle there; giving replies to those who repaired thither to propound fateful questions, as in the celebrated cave of Trophonius. Don Francisco, though he records this story, does not put faith in it: he gives it however as certain, that a Sacristan, named Clement Potosi, taught secretly the magic arts in that cave. Padre Feyjoo, who inquired into the matter, reports it as a vulgar belief, that the devil himself taught those arts there; admitting only seven disciples at a time, one of whom, to be determined by lot, was to be devoted to him body and soul forever. Among one of these sets of students was a young man, son of the Marquis de Villena, on whom, after having accomplished his studies, the lot fell. He succeeded, however, in cheating the devil, leaving him his shadow instead of his body. Don Juan de Dios, Professor of Humanities in the University, in the early part of the last century, gives the following version of the story, extracted, as he says, from an ancient manuscript. It will be perceived he has marred the supernatural part of the tale, and ejected the devil from it altogether. As to the fable of the Cave of San Cyprian, says he, all that we have been able to verify is, that where the stone cross stands, in the small square or place called by the name of the Seminary of Carvajal, there was the parochial church of San Cyprian. A descent of twenty steps led down to a subterranean Sacristy, spacious and vaulted like a cave. Here a Sacristan once taught magic, judicial astrology, geomancy, hydromancy, pyromancy, acromancy, chiromancy, necromancy, &c. The extract goes on to state that seven students engaged at a time with the Sacristan, at a fixed stipend. Lots were cast among them which one of their number should pay for the whole, with the understanding that he on whom the lot fell, if he did not pay promptly, should be detained in a chamber of the Sacristy until the funds were forthcoming. This became thenceforth the usual practice.