1. What Is Asana
Asana is steady, comfortable posture.
Patanjali Maharshi does not lay much stress on either Asanas or Pranayama. He has not mentioned about Kundalini also in any of the Sutras. Hatha Yogins have developed Asanas and Pranayama as a separate branch of Yoga later on. They pay much attention to Asanas and Pranayama to open the Kundalini. Hatha Yoga is a physical Yoga. Raja Yoga is a mental Yoga. Where Hatha Yoga ends, there Raja Yoga begins. Hatha Yoga and Raja Yoga cannot be separated. They are interdependent. Asana is the third Anga of Raja Yoga.
In Svetasvatara Upanishad (II-8), you will find: Keeping the upper parts, the chest, neck and the head erect and equal to the other parts of the body, subduing within the heart the senses together with the mind, let the wise by the raft of Brahman cross over all the fearful torrents of the world. Again in the Gita (VI-13) it is mentioned: Let him firmly hold his body, head, neck erect and still, gazing at the tip of his nose, and not looking around.
Greater emphasis is given in all the scriptures for keeping up the head, chest and body erect and steady. In the beginning stages of practice of concentration and meditation, the Sadhakas are particular to see that the head, neck, chest and body are erect. But later on, after a few minutes, the body begins to shake. Whenever the body is tossed, the mind also is disturbed. The trunk also begins to form a curve even without the knowledge of the Sadhakas. To avoid this trouble, the Rishis of yore have formulated four Asanas, viz., Siddhasana, Padmasana, Svastikasana and Sukhasana for practising Pranayama and Dhyana. Of the four Asanas, Siddhasana and Padmasana are very, very useful.
Sit on the ground over a blanket or a seat made of Kusha grass or a deer skin or a tiger skin. Spread the legs forward. Slowly bring the right foot and keep it over the left thigh. Then bring the left foot and carefully place it over the right thigh. Keep the head, neck and the trunk erect. Keep the hands on the knees. Or you can make a finger-lock and keep the locked hands over the left ankle. This is very convenient for some persons. Or you can place the left hand over the left knee and right hand over the right knee, palms facing upwards and the index finger touching the middle portion of the thumb. This is Chinmudra. If this posture, Padmasana, is not suitable, you can take recourse to Siddhasana.
Place one heel at the anus. Keep the other heel on the root of the generative organ. The feet or the legs should be so nicely arranged that the ankle joints should be in a line or touch each other. Hands can be placed as in Padmasana. This is Siddhasana. There are some other varieties in Siddhasana. Difference lies in keeping the heels. Refer to my book: Yoga Asanas.
2. How to Get Asanajaya
By mild and steady practice and meditation on the Infinite.
When you meditate on the Infinite, the mind is taken away from the body. Asana will become quite steady. If the mind becomes steady, the body also will become steady. Some take the word Ananta as the great serpent with 1000 heads which upholds the earth. If you meditate on the great serpent, then also the Asana will become steady. In Sutra 25 of Chapter III, you will find that a man gets the strength of an elephant by contemplating on the elephant. By contemplating on Hanuman, one gets the power of Hanuman. In the same way, if you contemplate on the steady Ananta that holds the earth, you will get the steadiness in posture.
If you can sit firmly in one Asana, then you have attained Asanajaya, mastery over posture. You will have to practise this gradually. First start with half an hour and then gradually increase the period. In three month's steady, regular practice, one can attain Asanajaya. When the Asana becomes steady you will not feel the body at all. You will experience great pleasure. If you sit in a posture that is not comfortable, then you may feel pain and the mind gets disturbed. Therefore in the previous Sutra a comfortable posture is prescribed.
3. Benefits of Asana
Then (when Asanajaya is obtained), (the practitioner) is free from the disturbance of the pairs of opposites.
The pairs of opposites are heat and cold, pleasure and pain, etc., which constitute all our worldly experiences. If you get mastery over one Asana, then only you are fit for taking up lessons in Pranayama and Dhyana.
Asana checks the wandering habits and removes Rajas and cures many kinds of diseases. One can easily concentrate and nicely meditate when the Asana has become firm and steady.
4. Instructions on Asanas
When you sit on the posture, think: I am as firm as a rock. Nothing can shake me. Give these suggestions to the mind a dozen times. Then the Asana will become steady soon. You must become a living statue when you sit for Dhyana. Then only you will be able to sit for three hours or even more at a stretch.
If there is pain in the legs after some time, stretch the legs and shampoo them for five minutes and again sit on the Asana. When you advance, you will not experience any pain. You will experience on the other hand immense joy. Never change the Asana like Padmasana for a few days and then Siddhasana for another few days and so on. Stick to one particular Asana and practise it regularly.
There are some other Asanas that are very useful such as Sirshasana, Sarvangasana, Paschimottanasana, Matsyendrasana, etc. Beginners should neglect all these because they are described in Hatha Yoga books. They are excellent Asanas for the preservation of good health and Brahmacharya. Without these two, viz., health and Brahmacharya, nothing can be done in the spiritual path. Students of Raja Yoga should have a steady and healthy mind. And so, the body also should be healthy and strong. These wonderful Asanas can be harmoniously combined up by Raja Yogic students also. I have seen many Sadhakas in a sickly condition with very poor physique and dilapidated constitution. They can simply close their eyes and sit like a statue. But they could not manipulate their minds in the proper direction and attain success in Raja Yoga.