95% sureThese words were traced back to where they first appeared. That source is listed below.
What turned up
On the Sphere and Cylinder, Book I, Assumption 1, c. 225 BC; trans. T. L. Heath, The Works of Archimedes (1897), p. 3.
Work
On the Sphere and Cylinder, Book I, Assumption 1; trans. T. L. Heath, 1897
Occasion
c. 225 BC · Syracuse, Sicily · the first assumption of his book on spheres and cylinders — the ancestor of 'a straight line is the shortest path'
Sources checked
archive.orgChecked using claude-fable-5, 22 August 2026Full djvu text read this pass; Assumption 1 verbatim in the treatise's own ASSUMPTIONS list (not Heath's commentary — his footnote calls it 'this well-known Archimedean assumption', citing Proclus). Complete standalone postulate; ancestor of the proverb 'a straight line is the shortest distance'.