Decades of Asia
In the first, published in 1552, de Barros relates the story of an embassy from the West African king of 'Benij' to Portugal, in which King João III is told about a powerful African king called Ogané. Because this Ogané was a powerful ruler in Africa and happened to carry a cross, the king believed this to be Prester John.
The second anecdote about Prester John contained within Decades of Asia "presents the standard case for Prester John being an Asian monarch, not Ethiopian" (Brewer, 288).