Date: 1714

"But when a monad has organs that are adjusted in such a way that, through them, there is contrast and distinction among the impressions they receive, and consequently contrast and distinction in the perceptions that represent them [in the monads] (as, for example, when the rays of light are conc...

— Leibniz, Gottfried Wilhelm (1646-1716)

Date: 1765

"Modern philosophers give them other fine names and Julius Scaliger, in particular, used to call them "seeds of eternity" and also "zopyra"--meaning living fires or flashes of light hidden inside us but made visible by stimulation of the senses, as sparks can be struck by steel."

— Leibniz, Gottfried Wilhelm (1646-1716)