Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 73
Sanskrit:
द्वितीयं च तथा मासं षष्ठे षष्ठेऽर्भको दिने ।तृणपर्णादिभि: शीर्णै: कृतान्नोऽभ्यर्चयन्विभुम् ॥ ७३ ॥
ITRANS:
dvitīyaṁ ca tathā māsaṁṣaṣṭhe ṣaṣṭhe ’rbhako dinetṛṇa-parṇādibhiḥ śīrṇaiḥkṛtānno ’bhyarcayan vibhum
Translation:
In the second month Dhruva Mahārāja ate only every six days, and for his eatables he took dry grass and leaves. Thus he continued his worship.