Chapter 6, Verse 21
Part of 6: Dhyān Yog — ध्यानयोगसुखमात्यन्तिकं यत्तद्बुद्धिग्राह्यमतीन्द्रियम्। वेत्ति यत्र न चैवायं स्थितश्चलति तत्त्वतः॥
sukham ātyantikaṁ yat tad buddhi-grāhyam atīndriyam vetti yatra na chaivāyaṁ sthitaśh chalati tattvataḥ
When he (the Yogi) feels that infinite bliss which can be grasped by the pure intellect and which transcends the senses, and is established therein, never moving away from the reality.
The Infinite Bliss of the Self (which is beyond the reach of the senses) can be grasped (realised) by the pure intellect independently of the senses. During deep meditation the senses cease to function, as they are involved into their cause, the mind. The intellect is rendered pure by the practice of Yama (selfrestriant) and Niyama (observances and disciplinary practices) and constant meditation.