पल्लव राजवंश के दौरान निम्नलिखित में से कौन सी मुख्य और स्थायी प्रशासनिक इकाई थी?

In Ancient Indian Statecraft, Kautilya's 'Rajamandala' theory primarily deals with:

The First Buddhist Council was held at ______.

Which ancient Indian text contains references indicating that population counts or census-like records were maintained in ancient India?