There are several theories about the first ascent of the Zugspitze. The chronological table on an 18th-century map describes the route along the path to the Zugspitze (ybers blath uf Zugspitze) and gives a realistic duration of 8.5 hours, so that it is reasonable to deduce that the summit had been climbed before 1820. The historian, Thomas Linder, believes that goatherds or hunters had at the very least penetrated to the area of the summit. It is also conceivable that smugglers used routes over the Zugspitze summit. As early as 1804 cartographic surveys had taken place in the area for the County of Werdenfels. There is speculation that, in the course of this work, the royal engineer and geographer, Alois von Coulon, had reached the summit. Since Coulon worked for the Topographical Bureau, it is unlikely that his ascent would not have been noted.