Man in the Iron Mask Dumas also presented a review of the popular theories about the prisoner extant in his time in the chapter "L'homme au masque de fer" in the sixth volume of his non-fiction "Crimes Célèbres". The earliest surviving records of the masked prisoner are from late July 1669, when Louis XIV's minister, the Marquis de Louvois, sent a letter to Bénigne Dauvergne de Saint-Mars, governor of the prison of Pignerol, which at the time was part of France. In his letter, Louvois informed Saint-Mars that a prisoner named "Eustache Dauger" was due to arrive in the next month or so. Louvois instructed
Man in the Iron Mask the enquiry the investigators were told about a supplier of poisons, a surgeon named "Auger", and Duvivier became convinced that Dauger de Cavoye, disinherited and short of money, had become Auger, the supplier of poisons, and subsequently Dauger, the man in the mask. In a letter sent by Louvois to Saint-Mars shortly after Fouquet's death while in prison (with Dauger acting as his valet), the minister adds a note in his own handwriting, asking how Dauger performed certain acts that Saint-Mars had mentioned in a previous correspondence (now lost) and "how he got the drugs necessary to do so". Duvivier