Note 089
From Chapter 2 of the Decline & Fall

In the time of Theodosius, Caesarius, a magistrate of high rank, went post from Antioch to Constantinople. He began his journey at night, was in Cappadocia (165 miles from Antioch) the ensuing evening, and arrived at Constantinople the sixth day about noon. The whole distance was 725 Roman, or 665 English miles. See Libanius Orat. xxii. and the Itineraria, p. 572-581.