Srimad Bhagavatam Canto 02, Chapter 02, Text 21

SB 2.2.21

tasmad bhruvor antaram unnayeta
niruddha-saptayatano ’napeksah
sthitva muhurtardham akuntha-drstir
nirbhidya murdhan visrjet param gatah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Thereafter the bhakti-yogi should push the life air up between the eyebrows, and then, blocking the seven outlets of the life air, he should maintain his aim for going back home, back to Godhead. If he is completely free from all desires for material enjoyment, he should then reach the cerebral hole and give up his material connections, having gone to the Supreme.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The process of giving up all material connections and returning home, back to Godhead, the Supreme, is recommended herein. The condition is that one should be completely freed from desire for material enjoyment. There are different grades of material enjoyments in respect to duration of life and sensual gratification. The highest plane of sensual enjoyment for the longest period of life is mentioned in the Bhagavad-gita (9.20). All are but material enjoyments, and one should be thoroughly convinced that he has no need of such a long duration of life, even in the Brahmaloka planet. He must return home, back to Godhead, and must not be attracted by any amount of material facilities. In the Bhagavad-gita (2.59) it is said that this sort of material detachment is possible to attain when one is acquainted with the supreme association of life. Param drstva nivartate. One cannot be freed from material attraction unless he has complete understanding of the nature of spiritual life. The propaganda by a certain class of impersonalists that spiritual life is void of all varieties is dangerous propaganda to mislead the living beings into becoming more and more attracted by material enjoyments. As such, persons with a poor fund of knowledge cannot have any conception of the param, the Supreme; they try to stick to the varieties of material enjoyments, although they may flatter themselves as being Brahman-realized souls. Such less intelligent persons cannot have any conception of the param, as mentioned in this verse, and therefore they cannot reach the Supreme. The devotees have full knowledge of the spiritual world, the Personality of Godhead and His transcendental association in unlimited spiritual planets called Vaikunthalokas. Herein akuntha-drstih is mentioned. Akuntha and vaikuntha convey the same import, and only one who has his aim fixed upon that spiritual world and personal association with the Godhead can give up his material connections even while living in the material world. This param and the param dhama mentioned in several places in the Bhagavad-gita are one and the same thing. One who goes to the param dhama does not return to the material world. This freedom is not possible even by reaching the topmost loka of the material world.
The life air passes through seven openings, namely two eyes, two nostrils, two ears and one mouth. Generally it passes through the mouth at the time of an ordinary man’s death. But the yogi, as above mentioned, who controls the life air in his own way, generally releases the life air by puncturing the cerebral hole in the head. The yogi therefore blocks up all the above-mentioned seven openings so that the life air will naturally burst forth through the cerebral hole. This is the sure sign of a great devotee’s leaving the material connection.
Srimad Bhagavatam Canto 02, Chapter 02, Text 20
Srimad Bhagavatam Canto 02, Chapter 02, Text 22