Book 1, Sutra 34: Patanjali’s Yoga Sutra
“OR WE CAN AVOID THE OBSTACLES AND PURIFY THE MIND BY A CONTROLLED EXHALATION FOLLOWED BY A RETENTION OF THE BREATH.”
Patanjali listed the obstacles that can create distraction in the mind of the yogic practitioner in sutras 30-31. In sutra 32 he recommended that we apply a single antidote to any obstacle that might arise. Sutras 33-39 list examples of such antidote practices. This sutra lists an advanced technique involving breath control.
Iyengar writes about this sutra’s instructions: “One should inhale and exhale slowly and pause, maintaining the retention for as long as possible. This practice ensures a state of consciousness which is like a calm lake.”