Srimad Bhagavatam Canto 07, Chapter 12, Text 25

SB 7.12.25

khe khani vayau nisvasams
 tejahsusmanam atmavan
apsv asrk-slesma-puyani
 ksitau sesam yathodbhavam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
A sober, self-realized person who has full knowledge should merge the various parts of the body in their original sources. The holes in the body are caused by the sky, the process of breathing is caused by the air, the heat of the body is caused by fire, and semen, blood and mucus are caused by water. The hard substances, like skin, muscle and bone, are caused by earth. In this way all the constituents of the body are caused by various elements, and they should be merged again into those elements.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
To be self-realized, one must understand the original sources of the various elements of the body. The body is a combination of skin, bone, muscle, blood, semen, urine, stool, heat, breath and so on, which all come from earth, water, fire, air and sky. One must be well conversant with the sources of all the bodily constituents. Then one becomes a self-realized person, or atmavan, one who knows the self.
Srimad Bhagavatam Canto 07, Chapter 12, Text 24
Srimad Bhagavatam Canto 07, Chapter 12, Text 26-28