Here's a fascinating treasury of information about historical esoteric research. I love this stuff because the lines between magic and science aren't at all clearly defined. For anyone who interested in history, in the occult, or, as I am, trying to invent systems of magic for gaming in Elizabethan England - this site is invaluable, and I'm sure it will be a great inspiration to my Swords Against Satan game. Take a look at the Twilit Grotto! However, be warned, you might have to break out Ye Olde Latin Textbook or use Google translate for some of it.