Talu is the term used in Yoga to mean palate both the hard and the soft palate. Talumula is the back side of the palate, which is at the spot between the eyebrows. This part has attained great importance in hatha yoga. It is said in Hatha Yoga Pradipika (III.77-82) that at the talumula the moon is situated in the human body. It secretes elixir, which trickles down the throat and goes as far as the sun, situated at the navel. The sun swallows that elixir and that is what causes old age. It is by doing inverted action (viparita karani) that one places the sun above and the moon down below; then the process of aging is stopped and thereby one can enjoy the vigor of youth permanently.
Talu assumes significance also with relation to another mudra called khecari, in which the tip of the tongue is turned back and inserted into the space above the talu. The space is called kapala kuhara, i.e., the space in the skull. Kapala kuhara is also called tripatha (junction of three paths) or vyoma cakra in Hatha Yoga Pradipika (III.37-41).
Khechari mudra is highly spoken of in the traditional texts and is said to have great esoteric value. It is said that one can even overcome death (mrityum jayati, III.44) by the practice of khechari mudra, by drinking the elixir secreted by the moon and not allowing it to reach the sun at the navel. At one place, khechari mudra is described as ‘inserting the tongue inside the talu’ (III.48-49). At the same place (III.51), it is recommended that both khecari and viparita karani mudras should be practiced simultaneously for better results.