SB 8.20.23
rasam acastanghri-tale ’tha padayor
mahim mahidhran purusasya janghayoh
patattrino januni visva-murter
urvor ganam marutam indrasenah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Thereafter, Bali Maharaja, who was occupying the seat of King Indra, could see the lower planetary systems, such as Rasatala, on the soles of the feet of the Lord’s universal form. He saw on the Lord’s feet the surface of the globe, on the surface of His calves all the mountains, on His knees the various birds, and on His thighs the varieties of air.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The universal situation is described herein in regard to the complete constitution of the Lord’s gigantic universal form. The study of this universal form begins from the sole. Above the soles are the feet, above the feet are the calves, above the calves are the knees, and above the knees are the thighs. Thus the parts of the universal body, one after another, are described herein. The knees are the place of birds, and above that are varieties of air. The birds can fly over the mountains, and above the birds are varieties of air.