The lightness, the feeling of the disappearance of the head and that all is open is a sign of the wideness of the mental consciousness which is no longer limited by the brain and its body sense—no longer imprisoned but wide and free. This is felt in the meditation only at first or with closed eyes, but at a later stage it becomes established and one feels always oneself a wide consciousness not limited by any feeling of the body.
Ref: Letters on Yoga – III