The Marquis Alexandre Saint-Yves d’Alveydre (1842-1909) is a key figure of French esoteric tradition who had a great influence on the magus Papus (who described Saint-Yves as his “intellectual teacher”) as well as Helena Blavatsky, Rudolf Steiner, and René Guénon. Saint-Yves also was the creator of the Archeometer, a measuring instrument, which he claimed was a “key” to understanding the Mysteries of the Word.