In 1487, after Prince Henry's attempts to find a sea route around Africa to lead to Prester John's east African kingdom had proved difficult, Portuguese King João II chose courtiers Pêro da Covilhã and Afonso de Paiva to travel via the Mediterranean and Egypt to Ethiopia to acquire knowledge of the origin of important spices, such as cinnamon, and to meet with Prester John. This mission was commissioned in parallel to that of Bartolomeu Dias, who was commissioned one year later to seek the Ethiopian kingdom by sailing around the southern tip of Africa (which he succeeded in doing in in 1488). Nonetheless, Pêro's mission became the most famous of all explorations into Africa to search for Prester John.
The Portuguese Covilhã, who was around 40 at the time, had spent much of his earlier life in Castile in the service of Don Juan de Guzmán, brother of Castilian Duke Enrique de Guzmán, but returned to Portugal when war broke out between Portugal and Spain. Covilhã's attached himself to King Afonso V and then to his son João II on the latter's ascendency to the throne in 1481. Covilhã's fluency in Arabic, Portuguese, and Castilian, along with his attested loyalty and reputed swordsmanship, made him a good candidate for this important diplomatic journey.
The resulting journey was arduous, full of twists and turns, and gave birth to several separate accounts, and the most authoratative, Francisco Álvares' True Information of the Lands of Prester John of the Indies (1526).
Silverberg admirably summarizes the complex journey (pp. 201-205):
In May 1487, Covilha and Paiva bade their sovereign farewell, receiving from him four hundred golden cruzados and a letter of credit that would be honored by any European banker. They went by way of Barcelona to Naples, thence to Rhodes, where, advised by some Portuguese who lived there to disguise themselves as merchants, they bought a cargo of honey. Then they sailed to Alexandria, where they both fell ill of fever; they seemed so close to death that the governor of the city, who was entitled to attach the property of foreiguers who died in Alexandria, confiscated their honey. Upon their unexpected recovery, they sued the overeager official for an indemnity, and, after a long delay, received some money with which they bought new goods. Going on to Cairo, they joined a party of Moorish merchants and in the spring of 1488 sailed with them down the Red Sea in an Arab dhow as far as Aden. There they parted, Paiva to go to Ethiopia while Covilha took passage for India in order to study the spice trade closer to its source. They agreed to meet eventually in Cairo.
Covilha, boarding an Arab ship, reached India after a month's voyage, landing at the port of Cananor. Journeying up and down the Malabar Coast, the resourceful Portuguese observed the activities of the Arab and Hindu spice merchants, learning of commodity prices, sources of supply, the prevailing winds governing tile shipping seasons, and much else. (Among his discoveries was the information that there was open sea beyond the southern tip of Africa, a fact that Bartolomeu Dias was independently learning about ti,e same time.) To confirm this news of a sea route around Africa, Covilha left India for Ormuz, the great mart on the Persian Gulf, and in 1489 headed by ship along the Arabian coast to East Africa. Reaching it well south of Ethiopia, he ventured as far as Sofala at 21 degrees S, some two thirds of the way down Africa's eastern shore; Arab traders were busy there, and he gained from them more details of the seaway around Africa, by which, he saw, Europe and the Orient could readily be linked. After collecting a wealth of data about harbors and sailing conditions in this part of Africa that would later be of immense value to Portugal, Covilha returned to Cairo, reaching it in 1490.
There was no sign of Paiva. A lengthy investigation revealed that Covilha's companion had lately arrived in Cairo from parts unknown in the last stages of a grave illness, and had died without telling anyone where he had been. At this news Covilha decided to go back to Portugal; but then he encountered two Portuguese Jews whom King Joao had sent to find him. They bore letters from the king reaffirming the importance of visiting the court of Prester John, and, since Covhilha had no way of knowing whether Paiva had succeeded in reaching Ethiopia, he realized it was necessary for him to go there himself. One of the Jews agreed to accompany him part of the way; the other received from Covilha a detailed account of his discoveries on the coasts of India and Africa, and carried it back to Portugal. Thus the information Covilha had gathered was made available to the coming generation of Portuguese explorers, who would make use of it in opening the hoped-for route to the Indies.
Covilha and his new companion, Rabbi Abraham, sailed to Aden; then, because the rabbi had business in Ormuz, Covilha escorted him there before turning toward Ethiopia. His progress toward Prester john was leisurely and indirect: he sailed to Jidda and then, disguised as a Moslem pilgrim, dressed in white and with his head shaved, he made the perilous journey to Mecca apparently just to satisfy his own curiosity; he went on even to Medina, and then to Sinai, where at the Monastery of St. Catherine he heard Mass for the first time since his departure from the Christian world four years before. At last, in 1493, he penetrated Ethiopia and presented himself to King Eskender (1478- 94), who greeted the ambassador from Joao of Portugal with great warmth. Flattered by the attention of an envoy from a brother Christian monarch of a distant land, Eskender promised to send Covilha back to his homeland laden with gifts and honors.
But Eskender died before Covilha was able to leave, and his brother Na'od (1494-1508) ascended the throne. Na'od treated Covilha graciously, but when the Portuguese ambassador reminded the king of his wish to go home, Na'od replied that it was not the custom of his land to allow foreign visitors to leave. And so Pero da Covilha's travels came to their end: he was marooned in the land of Prester John, like the painter Nicolo Brancaleone and a few dozen other Europeans who had happened to go to Ethiopia, and, like old Brancaleone, he was still there when the next ambassador from Portugal anrived at prester John's court in 1520. Francisco Alvares, a member of that ambassador's retinue, met Covilha and took down a full account of his adventures and of his quarter of a century in Ethiopia. According to Alvares, Covilha had applied to Na'od's Son and successor, King Lebna Dengel, for permission to depart, but this king also "would not give it, saying that he [Covilha] had not come in his time, and his predecessors had given him lands and lordships to rule and enjoy, and that leave he could not give him, and so he remains." Alvares relates that Covilha had been given "a wife with very great riches and possessions. He had sons by her and we saw them .... This Pero da Covilha is a man of great wit and intelligence and there is no one else like him at court; he is one who knows all the languages that can be spoken, both of Christians, Moors, Ethiopians, and heathens, and who got to know all the things for which he was sent; he gives an account of them as though he had them present before him. For this reason he is much liked by the Prester and all the court." When the new Portuguese envoys arrived, Alvares says, "a passionate desire to return to his country came upon him. He went to ask leave of the Prester and we went with him and we urged it with great insistence and begged it of him. Yet no order for it was ever given." Eventually the emissaries of 1520 were able to arrange their own departure from Ethiopia, but Covilha stayed behind, and remained in Prester John's land to the end of his life.