Democritus

Democritus ( dih-MOK-rih-təs; Greek: Δημόκριτος, Dēmókritos; c. 460 – c. 370 BC) was a pre-Socratic Greek philosopher from Abdera, primarily remembered today for his formulation of an atomic theory of the universe. Democritus wrote extensively on a wide variety of topics.

None of Democritus' original work has survived, except through second-hand references. Many of these references come from Aristotle, who viewed him as an important rival in the field of natural philosophy. He was known in antiquity as the ‘laughing philosopher’ because of his emphasis on the value of cheerfulness.

Notable works: quadratrix of Hippias

Source: Wikipedia — https://en.wikipedia.org/wiki/Democritus