This reconstruction is a device that works using an ingenious system of cogwheels of different sizes. Depending on which movement is made with the carriage, the cogwheels shift so that the pointer always points south. Such devices were probably manufactured from the middle of the 3rd century AD. With a chariot of similar size, these chariots were used for orientation visible from afar. (S. Nahser (in: Vermessen: Kartographie der Tropen), Berlin (Ethnologisches Museum), 2006, p. 31). Further reading: Needham, J.: Science and Civilisation, Vol 4, Cambridge, 1959, p. 286 ff