Among the nearly forty authors explicitly cited by Fra Mauro (active ca. 1430-ca. 1459/1464), Greek scientist Claudius Ptolemy (ca. 100-ca. 178), who lived in Alexandria in the 2nd century CE, is the one most mentioned and certainly the most important. Fra Mauro conceived and designed his map in pronounced opposition to Ptolemy’s Geography, a text which had been translated from Greek into Latin in Florence at the beginning of the 15th century. In highly complex cartouches of great value to the history of culture and science, Fra Mauro writes in first person, explaining that he could not limit his work merely to reproducing images from Ptolemy’s Geography, as many learned cosmographers of his era would have expected.

Instead, Fra Mauro insists that the vision of the world described by Ptolemy during the era of peak expansion of the Roman Empire had become obsolete for men of the mid-15th century. He emphasizes in particular that if he had followed Ptolemy, he would have had to exclude from his map many locations in the southern and northern parts of the oikumene. For these and many other localities—such as those described by Marco Polo (1254-ca. 1324), Odorico da Pordenone (ca. 1280-1331), and Niccolò de’ Conti (ca. 1395-1469)—specific longitudinal and latitudinal coordinates had not yet been confirmed, making it impossible to adopt Ptolemy’s cartographic structure. Although he openly declared his debt to and admiration for the great Alexandrine cosmographer, Fra Mauro analyzes Ptolemy critically, preferring instead a non-Ptolemaic method of representation.