वर्धन राजवंश (जिसे पुष्यभूति राजवंश भी कहा जाता है) की स्थापना किस शासक ने 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?