The first section of the sutras focuses on the idea of contemplation. These sutras define yoga as a practice of mental purification and controlling the unconscious and subconscious mind. In these sutras, five kinds of mental fluctuation (known as vrittis) are identified, which include knowing, erring, imagining, remembering and deep sleep. The first book of the sutras also contains the well known saying
“Yoga is the restraint of fluctuations of consciousness (vrittis)”
This shows how the focus of yoga is not only the physical workout we know it as today but also as an exercise of the mind whose focus is to be mentally neutral and without these fluctuations.