most important, as it extends all along the spinal cord and reaches into the head, sustaining the whole body. Vishnu is the deity whose power propels Sushumna according to verse 4.31. On both sides of the Sushumna reside the Ida and Pingala vessels, the former connected to the moon and the latter to the sun. These three drive the three Guṇas (forces behind the innate character) of a being, with Sushumna driving Sattva (goodness), Pingala driving the Rajas (action), and Ida driving the Tamas (destructiveness). These primary vessels are connected to numerous channels inside the human body, which pervade the whole body, and nourish it. When one inhales or exhales, according to verses 4.47–65, the Nadis are loaded with vital airs. There are ten types of vital airs, corresponding to different stages of breathing, and they are named Prana, Apana, Samana, Udana, Vyana, Naga, Kurma, Krikara, Devadatta and Dhananjaya. These affect the Nadis in different ways, and how the body functions and what the balance of organs within the body is, depends on food one takes in and how well inhalation and exhalation are able to deliver the vital airs to various body parts. The body interacts with nature, and removes liquids and excretes waste through nine holes. The aim of pranayama (breath control) is to purify the channels and nourish the inner body with vital airs. This benefits a yogi and yogini in preventing and curing diseases, as well as preparing the mind for meditation. Breath control and meditation for self-purification Chapters 5 and 6 discuss the means of cleansing the body and mind. The first ten verses of chapter 5 summarize and restate the need for always practicing virtuous self-restraints (Yamas), observances (Niyamas), avoiding anger against anyone or anything, truthfully following Dharma, respecting and learning from the Guru (teacher), and pursuing the proper goals of life without craving for rewards of one's action. Location for yoga Solitary places are the best venues for yoga. A matha (hut) in a forest is ideal, but any private place that is free from distractions, high winds or intense sunshine is a good location for yoga. Either a pad made of kusha grass or a solid ground with deer skin mat on it, is desirable. Yoga can be learned, with the help of a teacher, within three to four months if practiced six times a day. If frequent practice is not possible,