Reproduction of ancient travel sundial (Diptych Ars longa), in mahogany wood.
Instructions for use:

Opening the sundial at 90° orients the compass hand towards the north. The shadow cast by the wire on the dial will indicate solar time. When the upper dial has a sliding scale, you can determine the time at any latitude, the lead serves to verify that you are on a horizontal plane.
(inside the package there will be an explanation for how it works)

The sundial is the oldest instrument for measuring the time found. The term "sundial" indicates the type of sundial that marks only noon, that is, signals when the Sun is above the local meridian.
These instruments were already known in ancient Egypt, among the Greeks and Romans, the origin of this science is however even older and the first testimonies date back to the Neolithic.
In its minimal form it consisted of a prop planted in the ground, in the traditional one by a stylus called gnomon, which projected its shadow on a horizontal or vertical surface, called quadrant, indicating the astronomical time.

The Nuremberg diptych is a portable sundial, which saw its diffusion in the seventeenth and eighteenth centuries in Germany, through the production of many specimens, in wood, ivory and other materials, especially in Nuremberg where several families of gnomonist artisans resided.
The diptych consists of a rectangular box with a book opening, equipped with a compass inserted in the base for the orientation of the instrument in a north-south direction.
The time indicator is formed by a wire that is tensioned when the lid of the box is opened and is equivalent to the well-known polar stylus. The wire in many models can be moved to its upper attachment point, so as to allow the use of the instrument for multiple latitudes.
On the horizontal side, where the compass is inserted in a central position, circular or hexagonal time dials are usually reported, while a similar one is often, but not always, present on the vertical one.
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