चंद्रगुप्त मौर्य ने किस शासक को पराजित कर मगध पर मौर्य साम्राज्य की स्थापना की 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?