Archimedes' sunwidth reckoning
Illustration of Archimedes' (Sandreckoner 1.10-16) measurement of the Sun's angular width.
In the Sandreckoner (1.10-16), Archimedes describes how he measured the Sun's angular width. Place the cylinders close to or far away from the eye. Follow Archimedes' instructions (as displayed in the illustration), and you will also find upper and lower bounds for the Sun's angular width.