At first, Prester John was imagined to reside in India; tales of the Nestorian Christians' evangelistic success there and of Thomas the Apostle's subcontinental travels as documented in works like the Acts of Thomas probably provided the first seeds of the legend. After the coming of the Mongols to the Western world, accounts placed the king in Central Asia, and eventually Portuguese explorers convinced themselves that they had found him in Ethiopia, which had been officially Christian since the 4th century