In 1471 Fernando de Poo discovered the island which now bears his name, while in the same year Pedro d'Escobar crossed the equator.

Wherever the Portuguese investigators landed they left marks of their presence, at first by erecting crosses, then by carving on trees Prince Henry's motto, "Talent de bien faire," and finally they adopted the method of erecting stone pillars, surmounted by a cross, and inscribed with the king's arms and name.

These pillars were called _padraos_.
In 1484, Diego Cam, a knight of the king's household, set up one of these pillars at the mouth of a large river, which he therefore called the Rio do Padrao; it was called by the natives the Zaire, and is now known as the River Congo.

Diego Cam was, on this expedition, accompanied by Martin Behaim of Nuernberg, whose globe is celebrated in geographical history as the last record of the older views (p.
115).
Meanwhile, from one of the envoys of the native kings who visited the Portuguese Court, information was received that far to the east of the countries hitherto discovered there was a great Christian king.

This brought to mind the mediaeval tradition of Prester John, and accordingly the Portuguese determined to make a double attempt, both by sea and by land, to reach this monarch.