4 books
The science of breath and the philosophy of the tattvas Translated From the Sanskrit, With Introductory and Explanatory Essays on Nature S Finer Forces
The Science of Breath and the Philosophy of the Tattvas;
Patanjalis Yoga Sutras
The Yoga Darsana of Patanjali with Sankhya Pravacana Commentary of Vyasa and the Gloss of Vacaspati Misra