Yoga was born in India and the path of the Yogi is far removed from the yoga practiced in the west. Yoga was and still is followed by many as a path to Self Realization. Through specific practices and persistence, the Yogi is assured of achieving his goal.
In the west, we take asana as being yoga, however, that is the equivalent of going to church only for the singing. For some,singing is a joyful part of going to church, while it has nothing to do with the essence of going to church. It misses the point completely.
A Yogi follows a strict path of purification through adhering to certain guidelines in a way of knowing the Self. Patanjali, the Father of Yoga, wrote The Yoga Sutras as a moral compass for the Yogi to follow. The sutras direct the mind to finding itself through meditation, purification and freedom from outer desires. Knowing the Truth of Self illumines the mind that there is nothing to need and want as all is already One and perfect.
Many Gurus support the practice of yoga as a way of finding what is real and what is not. They teach non-duality through self-enquiry and believe that through earnest practice the Yogi cannot fail to achieve his goal of Self realization.
Through renouncing the ego the false belief in I, it is widely believed that the Truth will reveal itself. The ever-present witness that is always aware. The God aspect of everyone and everything that exists.
Patanjali recommends the practice of:
Non-violence in thought, word and deed.
Honesty in all aspects of life.
Non-lust In thought, word and deed.
Non-possessiveness warding against greed and desire.
He also states that there is a need for inner discipline and recommends:
Purity through practicing the above.
Contentment since no longer searching for outer fulfillment the Yogi can be content.
Austerity some go as far as living in what seems like poverty, however, austerity can also be of mind and body by having no desires.
Study of Sacred Texts.
Constant awareness of the Divine Devotion to your God/Guru.
Asana were traditionally used to warm the body for long sessions of meditation, and from looking at the above it is easy to see why asana were singled out as being preferable to the whole path. On first glance it seems very limiting to the self identified with the outside world and belief in separation. When one realizes that the above all point to discovering the God Self and awaking from the illusion of separation and ego, the above then makes more sense.
In all traditions, it is believed that God is within and not somewhere outside of us. Through the practice of Yoga it is possible to discover the God within, thereby realizing the Self and letting go of the limiting self beliefs that hold us back.