Patanjali and the Origins of Yoga Philosophy
Ashtanga Yoga Philosophy originates between 200 BCE to 250 CE with the Sage Patañjali. He compiled the existing yoga knowledge of his time and wrote a book called the Yoga Sutras. This book of 196 sutras, or verses, makes up what is commonly called "Classical" or "Raja" (Royal) Yoga.
The Classical definition of Yoga comes from Patanjali:
yogaścittavṛittinrodaḥ - Yoga is channeling or controlling the fluctuations of the citta.
The citta is the sum total of our: thoughts, desires, senses, emotions, personality, intellect, perception, memory, understanding, recognition and cognition. It consists of three parts: the sensory mind, ego, and intellect.
It is thought that learning to direct and control the citta allows us to see our True Self and gain direct experience of the Ultimate Reality. To achieve this objective, Patanjali defined 8 practices which are known as the Eight Limbs of Yoga. The term Ashtanga Yoga is found in the 2nd chapter of Patanjali's Yoga Sutras.