Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 1
Sanskrit:
मैत्रेय उवाचअथादीक्षत राजा तु हयमेधशतेन स: ।ब्रह्मावर्ते मनो: क्षेत्रे यत्र प्राची सरस्वती ॥ १ ॥
ITRANS:
maitreya uvācaathādīkṣata rājā tuhayamedha-śatena saḥbrahmāvarte manoḥ kṣetreyatra prācī sarasvatī
Translation:
The great sage Maitreya continued: My dear Vidura, King Pṛthu initiated the performance of one hundred horse sacrifices at the spot where the river Sarasvatī flows towards the east. This piece of land is known as Brahmāvarta, and it was controlled by Svāyambhuva Manu.