In the early part of the last century a series of very interesting experiments designed to demonstrate the effects produced upon a sensitive subject by the touch of precious stones and minerals, were made in the case of the “Seeress of Prevorst,” Frederike Hauffe (b. 1801), a woman believed to possess remarkable clairvoyant powers.[6] When pieces of granite, porphyry, or flint were placed in her hand, she was not affected in any way. The finest qualities of fluorspar, on the other hand, had a marked action, relaxing the muscles, causing diarrhœa, and producing a sour taste in the mouth; occasionally a somnambulistic state was induced. This latter condition was also produced by Iceland spar and by the sapphire. While the substances so far noted depressed the vital energy, sulphate of barium stimulated the muscles, produced an agreeable warmth of the body, and made the subject feel as though she could fly through the air. If the application of this material was long continued, the pleasurable sensation found expression in laughter. In the case of witherite, a carbonate of barium, this effect was produced to an even greater degree, for if water in which this mineral had been dipped were swallowed, spasms of laughter resulted. Rock-crystal also was found to possess a strongly stimulating influence, for if put in the hand, it aroused the subject from a half-slumber, and if placed on the pit of the stomach, it had the power to awaken the seeress from a somnambulistic trance, while at the same time an aromatic odor was diffused around. When, however, the application was continued for some time, the muscles stiffened, until finally an epileptic state ensued. Indeed, the rigidity produced was so great that the limbs resisted all attempts to bend them. The same effect, but in a much less degree, was caused by glass, even by looking at it, or by the tones emitted by a glass object when struck. All colorless silicates, the diamond, and even gypsum, had a similar effect, as did also heliotrope and basalt, either of which caused a bitter taste in the mouth.