- G. J. Toomer
Diodorus (4) of *Alexandria (1), mathematician and astronomer (1st cent. bce), wrote a work, Analemma, on the construction of plane sundials by methods of descriptive geometry. Only the section on the determination of the meridian from three shadow-lengths survives, in Latin and Arabic versions, but later treatments of the subject are found in *Vitruvius, *Heron, and *Ptolemy (4)'s Analemma (see mathematics). The work was important enough for *Pappus (see Collection 4. 246) to write a commentary on it. The Diodorus who commented on *Aratus (1)'s Phaenomena (see Aratea) may be the same man.