Francis Barrett
Author of "The Magus", published in 1801. An introduction to him and a short biography.
http://www.themystica.com/mystica/articles/b/barrett_francis.html

The Magus
The complete text including images.
http://www.sacred-texts.com/grim/magus/

The Mystica: Francis Barrett
A practically unknown author of "The Magus" published in 1801. This was a concise handbook on the occult and magic.
http://www.themystica.org/mystica/articles/b/barrett_francis.html

The Mansions of the Moon in the Magus
Listing of the 28 Mansions of the Moon and their use in electional astrology and magic from Francis Barrett's the Magus.
http://www.renaissanceastrology.com/mansionslistbarrett.html