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When practising kumbhaka, the breath should be retained without fear or shaking of the body. After completing the retention, exhale slowly and steadily, without any anxiety. Will power may be used to retain the breath, but the air should not be forced to remain inside by continuing the inhalation. One must not push one's limits. During the practice, prescribed ratios of inhalation, exhalation and retention should be followed.
During kumbhaka concentration can be achieved by focusing on a symbol, and the best symbol is light. While holding the breath, the light should be visualized at the eyebrow centre. If one is unable to visualize the light, trataka can be practised on a candle for some time prior to the practice. If the inner space becomes dark after practising kumbhaka, it is a negative symptom. However, if it becomes more and more illumined, it is a positive symptom.
The practice of kumbhaka should be undertaken when the ratios of inhalation and exhalation have been mastered. The nadis are purified in this way and become fit for sustained kumbhaka. The Yoga Chudamani Upanishad (v. 93) says that kumbhaka should be practised when the exhaled breath extends for twenty-six angulas (finger-widths). This distance can be measured easily by raising both hands in front of the face, so that the palms face downward with the fingers straight.
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