Zazzhu-dokei are Japanese Sundials. The fact that the gnomon had to point parallel to the axis of the Earth (direction of North Star at night) was known to Edo Period users. Sundials pre-date the Edo Period and were in common use until the mass production of Pocket Watches during the Meiji Period.

Apart from Inro-dokei and the later English Pocket Watch conversions, Wadokei were not portable. The average Japanese in the Tokugawa period carried pocket sun dials in the form of inro with netsuke to hang from the belt of their kimono. The inro usually consisted of a compass and a sun dial and were quite accurate timekeepers, provided the sun was shining.

Examples: From my collection.