Man in the Iron Mask one ever saw his face because it was hidden by a mask of black velvet cloth, the true identity of the prisoner remains a mystery; it has been extensively debated by historians, and various theories have been expounded in numerous books and films. Among the leading theories are those proposed by writer and philosopher Voltaire: he claimed in the second edition of his "Questions sur l'Encyclopédie" (1771) that the prisoner wore a mask made of iron rather than of cloth, and that he was the older, illegitimate brother of Louis XIV. What little is known about the historical Man in
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