मेहरौली का लौह स्तंभ, जो अपनी अत्यधिक जंग-रोधी संरचना के लिए प्रसिद्ध है, किस ऐतिहासिक काल से संबंधित है?

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?