"Patanjali's rules compel the student not only to acquire a right knowledge of what is and what is not real, but also to practice all virtues, and while results in the way of psychic development are not so immediately seen as in the case of the successful practitioner of Hatha Yoga, it is infinitely safer and is certainly spiritual, which Hatha Yoga is not. In Patanjali's Aphorisms there is some slight allusion to the practices of Hatha Yoga, such as "postures," each of which is more difficult than those preceding, and "retention of the breath," but he distinctly says that mortification and other practices are either for the purpose of extenuating certain mental afflictions or for the more easy attainment of concentration of mind. In Hatha Yoga practice, on the contrary, the result is psychic development at the delay or expense of the spiritual nature. These last named practices and results may allure the Western student, but from our knowledge of inherent racial difficulties there is not much fear that many will persist in them. (Preface)"