SB 4.8.73

dvitīyaṁ ca tathā māsaṁ
 ṣaṣṭhe ṣaṣṭhe ’rbhako dine
tṛṇa-parṇādibhiḥ śīrṇaiḥ
 kṛtānno ’bhyarcayan vibhum
Synonyms: 
dvitīyam — the next month; ca — also; tathā — as mentioned above; māsam — month; ṣaṣṭhe ṣaṣṭhe — every sixth day; arbhakaḥ — the innocent boy; dine — on days; tṛṇa-parṇa-ādibhiḥ — by grasses and leaves; śīrṇaiḥ — which were dry; kṛta-annaḥ — made for his food; abhyarcayan — and thus continued his method of worship; vibhum — for the Supreme Personality of Godhead.
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.