बुद्ध को ज्ञान की प्राप्ति निम्नलिखित में से किस वृक्ष के नीचे हुई 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?