Based on instruction from Liber ABA, Book 4, widely considered to be the magnum opus of 20th-century occultist Aleister Crowley. The most concise introduction to yogic meditation I've encountered, and in typical Crowley form, one of the least compromising. Traditional yet non-mystical, specific in its description of the progressively objective states of consciousness and the steps taken to attain them, it is evident that he is presenting what he has personally verified by experience.