Khecarī mudrā

Khecarī mudrā (Sanskrit, खेचरी मुद्रा) is a hatha yoga practice carried out by curling the tip of the tongue back into the mouth until it reaches above the soft palate and into the nasal cavity. The tongue is made long enough to do this with many months of daily tongue stretching and, in some versions of the practice, by gradually severing the lingual frenulum with a sharp implement over a period of months.

The goal is to attain liberation in the body, by sealing in the energy of bindu in the head so that it is not lost.