Ramayana
वरप्राप्तिं पितुस्ते तु ज्ञात्वेश्वरतपोबलात् । तपस्तप्तुं गता मेरुं भ्रातरः कृतनिश्चयाः ॥ 7-5-9 ॥
Having learned that their father had obtained his boon through the power of austerity directed to the Lord, the brothers, firm in their resolve, went to Mount Meru to perform austerities.
english translation