Nocturnal and Sundial
During the day, a person could tell time with this pocket-size device by unfolding a gnomon, a vertical shaft, and thereby turning the device into a small sundial. Turn it over at night, line it up with the pole star, Ursa Major, and it became a nocturnal. At night, the sky appears to revolve around the pole star, and though the stars’ positions vary by time of year, they can give an indication of time during the night. A nocturnal could be manipulated to help a person determine the local time based on these star positions. This nocturnal and sundial device dates to 1554.