Quṭb al-Dīn al-Shīrāzī's Textual Map of the Mediterranean Sea (1282) and Its Evident Source in a Portolan Chart.

In 1282, the Persian scholar, Quṭb al-Dīn al-Shīrāzī (d. 1311), included in a cosmographical work a description of a 'Greek' map of the Mediterranean. Rather than reproducing this map graphically, he placed a square grid over the image, listed the cells covered by the sea, and then itemised the toponyms according to their cell numbers. Once this pixelated map is created as he instructed, it is obvious that the 'Greek' map must have been an Italian portolan chart, featuring its unique elements: a realistic outline for the northern coast of Africa, especially the Gulf of Sirte, a simplistic rectangular form for the British Isles, a counterclockwise tilt, and a large size. With a toponymy that matches that on the oldest surviving portolan chart (the Carte Pisane, c.1270) and the next survivor (the Cortona chart), assigned to later that century, the 'Greek' map in Shīrāzī's possession in 1282 seems to be the second oldest portolan chart of which we have specific knowledge. This article recounts how a Persian cosmographer disseminated a cartographic image based on the direct observations of Christian pelagic mariners. This unexpected material evidence confirms that knowledge of those earliest accurate sea charts was not confined to the Latin world, even if such information exchanges were probably rare. [ABSTRACT FROM AUTHOR]