ARMAND-MARIE-JACQUES DE CHASTENET, MARQUIS DE PUYSÉGUR
Armand-Marie-Jacques de Chastenet, Marquis de Puységur (1751-1825), was a French aristocrat and military officer who became the most important magnetizer after Mesmer himself. An initiate of Mesmer’s Société de l’Harmonie, he carried the technique to his family estate at Buzancy, near Soissons, where in 1784 he observed that magnetizing some subjects produced not Mesmer’s convulsive crisis but a calm, sleep-like lucid state he called artificial (or magnetic) somnambulism. He set out the practice in his 1784 Détail des cures opérées à Buzancy, his Mémoires pour servir à l’histoire et à l’établissement du magnétisme animal, and the 1811 Recherches on somnambulism, and he founded the Société Harmonique des Amis Réunis at Strasbourg in 1785 to propagate it. His career was interrupted by the Revolution (during which he was imprisoned), and he revived his magnetic work in the 1800s and 1810s. He died in 1825 still defending the doctrine. The dates 1751-1825 are confirmed by the BnF, VIAF, GND, and Library of Congress authority records and by the Wellcome Collection’s catalogue authority for his works.