Four Asanas are prescribed for the purposes of Japa and meditation. They are Padma, Siddha, Svastika and Sukha.
You must be able to sit in any one of these four Asanas at a stretch for full three hours without shaking the body. Then only will you get mastery over the Asana (Asana Jaya). Then only can you take to the practice of Pranayama (control of breath) and Dhyana (meditation). Without securing a steady Asana you cannot further get on well in meditation. The more steady you are in your Asana the more you will be able to concentrate and make your mind one-pointed. If you can be steady in the posture even for one hour, you will be able to acquire one-pointed mind and feel thereby infinite peace and Atmic Ananda inside.
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 as a living statue when you sit for Dhyana. Then only there will be real steadiness in your Asana. In one year by regular practice you will have success and you will be able to sit for three hours at a stretch. Start with half an hour and gradually increase the period.
If there is severe pain in the legs after some time, unlock the legs and then shampoo them for five minutes and sit again in the Asana. When you advance you will not experience any pain. You will experience on the other hand immense joy. Practise the Asana both morning and evening.
After sitting in the Asana close eyes and concentrate on the Bhrukuti or Trikuti (the space between the two eyebrows) or in the Anahata Chakra (lotus of the heart). As the Trikuti (Ajna Chakra) is the seat of the mind, the mind can be quite easily controlled if you concentrate gently on this spot. Ekagrata (one-pointedness of the mind) supervenes quite readily. Concentration at the tip of the nose (Nasikagra Drishti), also has the same advantage, but it takes more time for the focussing of the mind. Those who cannot concentrate either at Bhrukuti or the tip of the nose may concentrate at any other outer point or inner Chakra of heart, head, neck, etc. Gazing at Trikuti (Ajna Chakra) is also called Bhrumadhya Drishti.
Keep the head, neck and trunk in one straight line. Stick to one Asana; either Padma, Siddha, Svastika or Sukha and make it quite steady and perfect by repeated attempts. Never change the Asana. Adhere to one tenaciously. Cling to it like a leech. Realise the full benefits of one Asana for meditation.
Books on Hatha Yoga eulogise the merits and advantages of Padma and Siddhasanas to a very high degree. He who sits in any one of the Asanas even for 15 minutes daily with closed eyes, concentrating on God at the lotus of the heart, destroys all sins and gets Moksha quickly. These Asanas increase digestive fire and give good appetite, health and happiness. They remove rheumatism and keep the three humours, wind, bile and phlegm in proper proportion. They purify and strengthen the nerves of the legs and thighs. They are suitable for keeping up Brahmacharya.