Shiva Purana

siva.sh/siva-purana/saturda-samhita/19/30

सोऽम्बरीषो नृपवरः सप्तद्वीपरसापतिः ।। नियमं हि चकारासावेकादश्या व्रते दृढम् ।। ३० ।।

sanskrit

The king Ambarīṣa was the lord of the earth consisting of seven continents. He observed the rite of Ekādaśī regularly with steady restraint.

english translation

so'mbarISo nRpavaraH saptadvIparasApatiH || niyamaM hi cakArAsAvekAdazyA vrate dRDham || 30 ||

hk transliteration by Sanscript