"We have seen that calculation of loxodromes involved the solution of a problem equivalent to the fundamental theorem of calculus. But that theorem was unknown to Europeans in the 16th c. How, then, did Mercator draw the chart? The abiding nature of the Mercator mystery is due to the fact that it cannot be appropriately solved within the framework of the Western historical narrative about the calculus. The mystery can be resolved by changing that narrative. It is hard to believe that Mercator drew his chart through sheer skill in draftsmanship. It is rather more likely that he had access to information from India or China, which he kept a secret. That this information was adequate to enable the calculation of loxodromes is evident from the fact that loxodromes were earlier used to map the zodiac, and a Chinese [Dunhuang] star map from ca. 950 follows the very same principle of isogonal cylindrical projection that has come to be known as the “Mercator” projection. This chart is reproduced in Needham’s volume."