At the invitation of King Manuel I of Portugal, Amerigo Vespucci—a Florentine who had been working for a branch of the Medici Bank in Seville since 1491, fitting oceanic expeditions and travelling twice to The Guianas with Juan de la Cosa in the service of Spain—participated as observer in these exploratory voyages to the east coast of South America. The expeditions became widely known in Europe after two accounts attributed to him, published between 1502 and 1504, suggested that the newly discovered lands were not the Indies but a "New World", the "Mundus novus"; this is also the Latin title of a contemporary document based on Vespucci letters to Lorenzo di Pierfrancesco de' Medici, which had become widely popular in Europe. It was soon understood that Columbus had not reached Asia but had found a new continent, the Americas. The Americas were named in 1507 by cartographers Martin Waldseemüller and Matthias Ringmann, probably after Amerigo Vespucci.