Obeliscus Aegyptiacus

[...he] taught mathematical disciplines, handed down to men the order of times, and the law and political reason for living well and happily; and it came to pass that all men illustrious for knowledge and discipline were named famous Adris after him, because he was the first to have disputed concerning all knowledge and doctrine.

He says that he discovered letters in the likeness of animals, which we call hieroglyphs, and the Copts themselves also testify to this; indeed, the author of our great Coptic Onomastic Scale, where he treats of the figures of the letters and their origin, writes thus in Coptic:

Egypt, he says, derived its first characters from the figures of animals.

Moreover, Mor Isaac, in his Syriac Philosophy, series 2, chapter 2, calls Hermes Adris—Trismegistus, that is, "thrice-great," because of the threefold office he discharged:

Hermes, wise in all things, was himself great for a threefold reason, for he was a Prophet, a Priest, and a philosopher.

And from this accumulation of testimonies it is clearly evident that the hieroglyphic letters were invented by Hermes not to signify histories, as many falsely persuade themselves, or eulogies of Kings, and similar things, but rather the most profound mysteries of the Divinity; so that, consequently, unless the wise Priests revealed them, it would be considered a huge sin. These things indeed having been premised, let them now return to our intention.