After sitting on your seat, practice the three kinds of breathing exercises, and thus gradually control the life air, the mind and the senses. Completely free yourself from all material contamination, and with great patience begin to meditate on the Supreme Personality of Godhead.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
प्राणायामेन त्रिवृता प्राणेन्द्रियमनोमलम् । शनैर्व्युदस्याभिध्यायेन्मनसा गुरुणा गुरुम्
prāṇāyāmena trivṛtā prāṇendriyamanomalam | śanairvyudasyābhidhyāyenmanasā guruṇā gurum
SB 4.8.44