Franz Anton Mesmer, a Vienna-trained physician working in Paris from the 1770s, proposed that a single invisible fluid, which he called animal magnetism to distinguish it from ordinary mineral magnetism, pervaded the universe and connected all living bodies, and that disease resulted from blockages in this fluid's natural flow through the body, blockages a trained magnetizer could detect and clear. Mesmer's most famous treatment setting was the baquet, a large covered tub filled with iron filings, powdered glass and bottles of magnetized water, from which iron rods projected for patients, seated in a circle around it and often holding hands, to apply to their afflicted body parts, while Mesmer himself, dressed dramatically in lilac silk, moved among them making hand passes and using a wand or his own touch to direct the fluid.
Treatment frequently produced dramatic "crises," convulsions, weeping, laughter or fainting, which Mesmer and his followers interpreted as the therapeutic climax of the fluid's blockage being released, after which patients often reported genuine relief from their symptoms. Mesmer's clinic became immensely fashionable in pre-revolutionary Paris, drawing aristocratic clients and considerable controversy among the city's established medical faculty, who viewed his claims and his showmanship with open suspicion well before any formal investigation was convened.