Thoth invented the Egyptian picture-writing called hieroglyphs. Some of the oldest hieroglyphic texts claim Thoth as their author, including the famous Egyptian Book of the Dead. The priests of Thoth claimed to have secret texts authored by Thoth that contained magic instructions.
Place provides the most comprehensive account of Thoth as divine originator of sacred writing, secret knowledge, and magic, and traces how this figure gave rise to the legend of the Book of Thoth and its eventual identification with the Tarot.
, The Tarot: History, Symbolism, and Divination, 2005thesis