(Śiva Saṁhitā): This scripture is one of the three classic texts of Hatha Yoga (along with the Hatha Yoga Pradipika and the Gheranda Samhita), and is considered the most comprehensive. Its author is unknown, as is its date of publication—it was commonly believed to have been written in the seventeenth or eighteenth centuries, but more recent research suggests that it was written before 1500 A.D. The text presents yoga philosophy and emphasizes that even householders can benefit from its practice. Among other things, it describes the nadis and the subtle anatomy, mentions eighty-four yoga asanas, describes the five types of prana (as well as techniques to regulate them), and introduces several mudras for spiritual transformation.