Full Idea
Anaximander said that the first principle and element of existing things was the boundless; it was he who originally introduced this name for the first principle.
Gist of Idea
Anaximander introduced the idea that the first principle and element of things was the Boundless
Source
report of Anaximander (fragments/reports [c.570 BCE], A09) by Simplicius - On Aristotle's 'Physics' 9.24.14-
Book Reference
'The First Philosophers', ed/tr. Waterfield,Robin [OUP 2000], p.14
A Reaction
Simplicius is quoting Theophrastus