Mbh 9.37.3a

Vaishampayana said, "Formerly, in the Krita age, O king, the ascetics dwelling in Naimisha were engaged in a grand sacrifice extending for twelve years. Many were the Rishis, O king, that came to that sacrifice. Passing their days, according to due rites, in the performance of that sacrifice, those highly blessed ones, after the completion of that twelve years' sacrifice at Naimisha, set out in large number for visiting the tirthas. In consequence of the number of the Rishis, O king, the tirthas on the southern banks of the Sarasvati all looked like towns and cities. Those foremost of Brahmanas, O tiger among men, in consequence of their eagerness for enjoying the merits of tirthas, took up their abodes on the bank of the river up to the site of Samantapanchaka. The whole region seemed to resound with the loud Vedic recitations of those Rishis of cleansed souls, all employed in pouring libations on sacrificial fires. That foremost of rivers looked exceedingly beautiful with those blazing homa fires all around, over which those high-souled ascetics poured libations of clarified butter. Valkhilyas and Asmakuttas, Dantolakhalinas, Samprakshanas and other ascetics, as also those that subsisted on air, and those that lived on water, and those that lived on dry leaves of trees, and diverse others that were observant of diverse kinds of vows, and those that forswore beds for the bare and hard earth, all came to that spot in the vicinity of the Sarasvati. And they made that foremost of rivers exceedingly beautiful, like the celestials beautifying (with their presence) the heavenly stream called Mandakini. Hundreds upon hundreds of Rishis, all given to the observance of sacrifices, came thither. Those practisers of high vows, however, failed to find sufficient room on the banks of the Sarasvati. Measuring small plots of land with their sacred threads, they performed their Agnihotras and diverse other rites.