Though the book where I picked it up from says it is a forehead pose and nothing else, I believe it must be named after sage Kapila, who is a bhakti yogi, who describes the cosmic energy in a very interesting way. He is said to explain this to his mother, Devahuti, who attains mokhsha on hearing his description:) He says this energy can see with its feet..
I borrowed this from this site, an explanation from Swami Krishnananda on Kapila's discourse with his mother:
"In the case of an ordinary mortal, there is a distinction made between the functions of the head, heart, lungs, feet, hands and so on, but in the case of the Mighty Person, such distinction is not made. Any part is as good as any other part. We cannot say that His feet are inferior to His head, as no such comparison is possible in the case of God’s Personality. His limbs are described for the purpose of meditation. Every part is capable of doing the function of any other part. This is how we have it in the Bhagavadgita or in the Veda. Sarvataḥ pāni-pādam tat sarvato’kṣi-śiro-mukham, sarvataḥ śrutimal loke sarvam āvṛtya tiṣṭhati (13.13): Every part of His body are eyes and ears, every part is mouth, every part is feet, every part is hands. He can work with His feet, not merely with His hands; He can see with His toes and speak with His nose, because every function is an attribute of every part of God. It is not a limitation of concept as in our own personality where one organ cannot know the function of another organ. There, every organ is all organs because God is called All-in-all.
So Padadikeshantavarnana is the subject of this description for the purpose of meditation. "
I must I did not stay long enough in the Kapilapose to be able to experience this:( It puts a lot of scrunch on the neck itself and can be very demanding for a long hold.. but I believe it could ultimately help you reach the no-hands headstand/..
What this pose needs:
- A basic ability to take a fall in the headstand! No jokes, because to stay up on the forehead could be tricky. Even more, when you throw one leg back, as suggested, it can topple you back, since the whole back is now curved, almost towards a complete fall or release from the headstand.
- Neck strength and flexibility.
- It creates quite a cramp at the back of the thighs, so that could be rather unexpected..