I’ll take the next few Posts to layout the founding texts. The principal sources which bridge the first intuition of Shūnyam in the Rig Vedam to its final functional formulation as the Self-Negating Expression unwound in an ‘Infinite Regress’, the ‘Backward Step’ that necessarily converges on ‘ True Nothing’.
The two core texts are the Bṛhadāraṇyaka Upaniṣad and the Vajracchedikā [‘Diamond’] Sūtra.
The two ancillary texts are the Chandogya Upaniṣad [along with the Bṛhadāraṇyaka, the second of the two oldest extant texts in the Upaniṣadic canon] and the Hṛdaya [‘Heart’] Sūtra [ incorrectly and commonly interpreted as a summary of the ‘Diamond’ Sūtra].
The four texts span a period of over 800 years ending around 200 BCE, their content revealing an evident continuum.
Once done with that, I’ll get to the method to get to Shūnyam.