Johannes Trithemius
“This is Trithemius’ most notorious work. On the surface it is a system of angel magic, but within is a highly sophisticated system of cryptography. It claims to contain a synthesis of the science of knowledge, the art of memory, magic, an accelerated language learning system, and a method of sending messages without symbols or messenger. In private circulation, the Steganographia brought such a reaction of fear that he decided it should never be published. He reportedly destroyed the more extreme portions (presumably instructions for prophecy/divination) but it continued to circulate in mss form and was eventually published posthumously in 1606.”