The invention of postal relay

[timelets]

“There is nothing that travels faster, and yet is mortal, than these couriers; the Persians invented this system, which works as follows. It is said that there are as many horses and men posted at intervals as there are days required for the entire journey, so that one horse and one man are assigned to each day. And neither snow nor rain nor heat nor dark of night keeps them from completing their appointed course as swiftly as possible. The first courier passes on the instructions to the second, the second to the third, and from there they are transmitted from one to another all the way through, just as the torchbearing relay is celebrated by the Hellenes in honor of Hephaistos. The Persians call this horse-posting system the angarcion.”

Herodotus, Histories.