Medici-Laurentian Atlas

The atlas is explicitly dated 1351 (as per its astronomical calendar), but scholars believed it was more likely composed around 1370, possibly from earlier material, and probably amended further later, with emendations as late as 1425–50.

Nearly a century before the Portuguese Age of Discovery, the Medici atlas draws the bend of the Gulf of Guinea and shows that Africa has a southern end, i.e. that the Atlantic and Indian Oceans are connected to each other below the African continent.

[2] The probable source of the "Guinea bend" is the legend of the Sinus Aethiopicus, the rumor of a gulf that lay somewhere south of Cape Bojador that was said to penetrate deeply into the African continent.

The notion that the West African coast did not extend straight south but took a sharp eastward bend, could be a hazy reference to the actual Gulf of Guinea, but more probably it was just a lucky guess and a bit of wishful thinking.

(Historian Russell[6] notes that the Portuguese Prince Henry the Navigator was entranced by the legend of the Sinus Aethiopicus, as it held out the prospect of a direct sea route around West Africa to the Christian kingdom of Prester John (Ethiopian Empire), avoiding the complications of travelling through the Muslim lands of Egypt to reach it.

Long before the Medici map, the Vivaldi brothers of Genoa, in 1291, had tried to sail down the west African coast, with the explicit objective of trying to find a sea route to Asia.

[8] The Medici Atlas shows most of the main Canary islands, excellently delineated (if not yet fully named), greatly improving upon the couple in the 1339 Angelino Dulcert map.

These Azores islands appear with these names in two subsequent Majorcan maps - the 1375 Catalan Atlas and the 1385 map of Guillem Soler, with some more detailed sorting of the groups, e.g. Medici's "Ventura Sive de Columbis" label is broken into three distinct names: "San Zorzo" ("St. George", S. Jorge), Ventura (Faial) and Li Columbis (Pico); and the pair of "Corvis Marinis" are distinguished between Corvis Marinis (Corvo) and Li Conigi ("rabbits", Flores).

The anonymous Castilian author of the Libro del Conoscimiento also supplies these names, breaking up the southerly Cabrera group (which the Catalan forgot) into the islands of las cabras ("goats", S. Miguel) and lobo ("seals"?

One (unproven) possibility is that the Azores were indeed discovered, or at least seen from a distance, quite by accident, by the aforementioned 1341 mapping expedition on their return via a long sailing arc (volta do mar) from the Canary islands.