Agreed. Interestingly, my understanding is that it was quiet-ishly passed on by monks and clergy through the middle ages. See John of Morigny on Wikipedia as an example.
Interesting example, I hadn't heard of Morigny, and will look at his book.
I think one reason these things are 'mystical' and 'mysterious' is because the people that understood them did openly talk about them and write about them, but used literary and speaking techniques that give them plausible deniability, and mostly limit the audience to people intelligent enough to decipher them. William Blake is a great example of this- he was writing about ideas so progressive and ahead of their time, many are still today unacceptable to talk about, yet he was able to publish book after book about them in the late 1700s, and was regarded as kooky, rather than dangerous.
