The Société de l’Harmonie Universelle represents the nucleus of the mesmerist movement, whose influence on the eve of the French Revolution has already been demonstrated by the works of Robert Darnton. By reexamining the original sources, it is possible to reconstruct the composition and the vicissitudes of this organization, thereby nuancing the traditional image of a group polarized between a restrained radical tendency and an aristocratic, conservative majority. Many of its members, indeed, are found in the network of pre- Revolutionary sociability, as well as in the Constituent Assembly, where theywere divided among different political options. Certain deputies continued to the practice animal magnetism and somnambulism. In political debates, mesmerism was usually associated with Charlatanism and the Old Regime. Yet in the discourse of the constituents, whether with Bergasse or Malouet, Gouy d’Arcy or Duport, several traces of mesmerist doctrines and experiences are recognizable.