It is said that as many days as there are in the whole journey, so many are the men and horses that stand along

the road, each horse and man at the interval of a day’s journey; and these are stayed neither by snow nor rain

nor heat nor darkness from accomplishing their

appointed course with all speed.

                                          — Herodotus, Histories (8.98) (trans. A.D. God ley, 1924)