Ṣaṭ-cakra-nirūpaṇa

The Bengali Sanskrit text describing six wheels along the spine with their petal-counts, seed-syllables, elements and presiding deities. Its date is disputed in the scholarship — most say 1577, some 1526 — and this app reports the disagreement rather than picking a side.

The whole modern chakra system descends from here, and here is late-medieval Bengal. Not Vedic. Not Upaniṣadic. Not "five thousand years old." And it is one scheme among competitors — other Tantric texts count four wheels, or five, or nine, or twelve, because these are models of a practice and not a published anatomy.