Mbh 5.189.1b

Devoted to the good of myself--their well-wisher, those spies of mine, with great application brought to me accounts of her course of action, her words and actions, from day to day. When that maiden went to the woods, resolved on ascetic austerities, even then I became melancholy, and afflicted with pain, I lost my heart’s tenor. Except one acquainted with Brahma and observant of vows, that are praiseworthy owing to the austerities they involve, no Kshatriya hath ever by his prowess, vanquished me in battle! I then, O king, humbly represented to Narada as also to Vyasa all that the maiden did. They both told me, ‘O Bhishma, do not give way to sorrow on account of the daughter of Kasi. Who is there that would venture to baffle destiny by individual exertion?’ Meanwhile, O great king, that maiden, entering a cluster of retreats practised austerities, that were beyond human powers (of endurance). Without food, emaciated, dry, with matted-locks and begrimed with filth, for six months she lived on air only, and stood unmoved like a street-post. And that lady, possessed of wealth of asceticism, foregoing all food in consequence of the fast she kept, passed a whole year after this, standing in the waters of the Yamuna. Endued with great wrath, she passed the next whole year standing on her front toes and having eaten only one fallen leaf (of a tree). And thus for twelve years, she made the heavens hot by her austerities. And though dissuaded by her relatives, she could not by any means be weaned off (from that course of action). She then went unto Vatsabhumi resorted to by the Siddhas and Charanas, and which was the retreat of high-souled ascetics of pious deeds. Bathing frequently in the sacred waters of that retreat, the princess of Kasi roamed about according to her will.