sanas originated in India. In his Yoga Sutras, Patanjali (c. 2nd to 4th century CE) describes asana practice as the third of the eight limbs (Sanskrit: अष्टाङ्ग, aṣṭāṅga, from अष्ट् aṣṭ, eight, and अङ्ग aṅga, limb) of classical, or raja yoga.
What is the third limb of yoga?
The third limb of yoga is know as Asana.  This refers to the physical practice of yoga, or the yoga postures.  By putting the body into difficult positions you achieve several key benefits. The first is you are helping your body heal pain.  If you want to meditate and work on healing your mind, you need to first heal your body.  Otherwise your easily distracted mind will focus on pain in your body versus the pain in your mind.  Secondly, commitment to the Asana will teach you the discipline your mind needs to heal.  When going into uncomfortable situations, bad patterns in the mind often arise.  Stepping into discomfort actually becomes an opportunity to study the mind and change patterns of response.