He taught, if he did not discover, the obliquity of the ecliptic, is said to have introduced into Greece the gnomon (for determining the solstices) and the sundial, and to have invented some kind of geographical map. But his reputation is due mainly to his work on nature, few words of which remain.
His Lectiones in omnes Psalmos Davidis (1635) is exceedingly suggestive and terse in its style, reminding of Bengel's Gnomon, as does also his Commentarius utriusque Epist.
When not in use the gnomon is folded downwards and stored inside the cylinder.
Nearly all sundials have a gnomon (which casts the shadow) pointing to the Celestial Pole.
It too incorporates the splint gnomon giving the light of light at every noontime.