In the tantrik tradition, each aspect of devata has her or his own form of the Gayatri and it is often pronounced at the four junctions of the day, including midnight. Tripurasundari vidmahe, kameshvari dhimahi, tanno klinne pracodayat. The Gandharva Tantra uses the 24 different syllables of this mantra in Sanskrit as a visualisation, starting from the base of the spine and moving to the top of the head. The other tantrik Gayatri is a mantra known as Ajapa. This is recited by every living being unconsciously 21,600 times a day as she or he breathes.
Half are sun breaths and half are moon breaths.
It consists of the letters Ha and Sa.