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 in the work 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 are, indeed, to be found in the networks of pre-Revolutionary sociability, as well as in the Constituent Assembly, where they were divided among different political options. Certain deputies still followed the practice of animal magnetism and somnambulism. In political debates, mesmerism was usually associated with Charlatanism and the Old Regime; nevertheless in the discourse of the Constituents, whether that of Bergasse or Malouet, Gouy d’Arcy or Duport, several traces of the doctrines and mesmerist experiences are recognizable.