Anahata (the 'unstruck') is the fourth chakra, located at the hridaya (heart center), where the anahata-nada — the primordial sound that resonates without any physical striking — is perceived by the advanced yogi. The Sat-Cakra-Nirupana describes it as a twelve-petaled lotus of deep red, governed by the vayu tattva (air element) with the bija mantra YAM. It is the seat of the jivatman (individual self) and the junction where the three lower chakras of pravritti (worldly engagement) meet the three upper chakras of nivritti (spiritual withdrawal). The Chandogya Upanishad's teaching of the dahara-vidya — the meditation on the tiny space within the heart that contains the entire cosmos — maps precisely to Anahata's function as the bridge between finite self and infinite Brahman.