A large circular tub that figured prominently in the magnetic treatment that Charles d'Eslon, a friend and follower of Franz A. Mesmer 's, prescribed for his patients. The marquis of Puységur tells us in his book Du Magnétisme Animal (1807) that some bottles, arranged in a particular manner, were placed in the baquet and partly covered with water. The tub was fitted with a lid having several holes through which passed iron rods connecting the patients, who sat around the contrivance. The operator was armed with a shorter iron rod. While the patients waited for a response to the treatment, someone played a pianoforte, a device frequently used at Spiritualist séances. Reactions included violent convulsions, cries, laughter, and vomiting. This state, called the crisis, was supposed to hasten the healing process.
A commission appointed in 1784 by the French government to report on mesmerism suggested that such practices were exceedingly dangerous and in no way proved the existence of an alleged magnetic fluid.
Harte, Richard. Hypnotism and the Doctors. I. Mesmer/De Puységur. London: L. N. Fowler, 1902.