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They are difficult to master and are intended only for the serious sadhaka. The practitioner who becomes competent in all the stages of beginner and intermediate levels will gain the full benefit of the practice, physically, mentally and spiritually. Progress beyond this point is sadhana to be undertaken only under the strict guidance of a master.
General guidelines Posture: One may assume postures such as sukhasana, ardha padmasana and vajrasana during the preliminary stages, but in the more advanced stages these postures will not lock the body and keep it steady. Therefore, it is better to choose one of the locked meditative postures such as siddhasana, siddha yoni asana, padmasana or swastikasana. Advanced stages of kumbhaka with ratio and bandhas should not be attempted unless one steady posture can be held comfortably throughout the practice. Any kind of tension will block the free flow of prana and distract the awareness. One should check the sitting position periodically to see that the back, neck and head remain straight, steady and still. There should be no shaking or nervous tremors in any part of the body
Stages of practice: Four techniques are described here with progressive stages in each, which allow for a smooth development from beginning to advanced levels. However, this is intended to take place over a long period of time. Each stage should be practised for at least two weeks before proceeding to the next. Mastery of some stages may take months, and there should not be any hurry. More benefit can be obtained by perfecting the details of breathing than by achieving advanced stages. Control of the respiratory system requires gradual development. Time is needed for the body and mind to adjust to the effect of extended breath and retention.
Familiarity with the techniques of expanding the breath capacity (see Chapter 16: 'Preliminary Breathing Practices') will enable one to practise each new stage of nadi shodhana through both nostrils, before proceeding to alternate nostril
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