For more than 260 years, the contents of that page--and the details of this ritual--remained a secret. They were hidden in a coded manuscript, one of thousands produced by secret societies in the 18th and 19th centuries. At the peak of their power, these clandestine organizations, most notably the Freemasons, had hundreds of thousands of adherents, from colonial New York to imperial St. Petersburg. Dismissed today as fodder for conspiracy theorists and History Channel specials, they once served an important purpose: Their lodges were safe houses where freethinkers could explore everything from the laws of physics to the rights of man to the nature of God, all hidden from the oppressive, authoritarian eyes of church and state. But largely because they were so secretive, little is known about most of these organizations. Membership in all but the biggest died out over a century ago, and many of their encrypted texts have remained uncracked, dismissed by historians as impenetrable novelties.