In alchemical/magical tradition, powerful secrets of alchemy were found inscribed on an emerald tablet in the hands of the mummy of Hermes Trismegistus, the master magician and alchemist, who had been entombed in an obscure chamber of the Great Pyramid of Giza. The preamble to the key to transmuting base materials to precious metals and gems instructed the adept that "It is true, without falsehood, and most real: that which is above is like that which is below, to perpetrate the miracles of one thing." The writings of Hermes Trismegistus were considered by the alchemists as a legacy from the master of alchemy and were, therefore, precious to them.
As much as the thought of such a find may fire the imagination, the discovery of the Emerald Tablet at Giza is quite likely an allegory. The alchemists, who were concerned with the spiritual perfection of humankind as well as the transmutation of base metals into gold, commonly recorded their formulas and esoteric truths in allegorical form. Today it is known that there was no single personage named Hermes Trismegistus and that the Leyden Papyrus discovered in the tomb of the anonymous magician contains the oldest known copy of the inscription from the legendary Emerald Tablet, which is itself a description of the seven stages of gold-making.
Hermes, who is called Trismegistus, "three times the greatest," was a deity of a group of Greeks who once founded a colony in Egypt. This transplanted god drew his name from Hermes (Mercury to the Romans), the messenger of the Greek hierarchy of deities and the god who conducted the souls of the dead to the underworld kingdom of Hades. The Egyptians identified Hermes Trismegistus with Thoth, who, in their pantheon of gods, was the divine inventor of writing and the spoken word. These same Greek colonists developed an interest in the old Egyptian religion, then went on to combine elements of their hellenistic beliefs, add fragments of Judaism and other Eastern belief constructs, and set about creating a synthesis of the various theologies. A vast number of unknown authors worked at the great task of composing a series of esoteric writings, all of which were attributed to the mythical figure of Thoth-Hermes. Eventually, Thoth-Hermes became humanized into a legendary king, who supposedly wrote the amazing total of 36,525 volumes of metaphysical teachings. In the third century, Clement of Alexandria reduced the total to 42, which he said he saw in a vision being carried by adepts.