At the base of the central support beam of the spire, an iron plaque dedicated to the achievement of the workers was inscribed with the image of a compass and a try square. These were the symbols of the mason's guild and a subtle reference to God's role as Great Architect of the Universe in Catholic tradition. Because both Viollet-le-Duc and Bellu are both mentioned by name on the plaque, it has been theorized that they were Freemasons.« Viollet-le-Duc et le compagnonnage : La flèche de la cathédrale Notre-dame de Paris », on hermetism.free.fr.(in French).
