सुमात्रा द्वीप पर केंद्रित कौन सा प्राचीन हिंदू साम्राज्य स्थित था?

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?