A periplus , or periplous, is a manuscript document that lists the ports and coastal landmarks, in order and with approximate intervening distances, that the captain of a vessel could expect to find along a shore. In that sense, the periplus was a type of log and served the same purpose as the later Roman itinerarium of road stops. However, the Greek navigators added various notes, which, if they were professional geographers, as many were, became part of their own additions to Greek geography.
The form of the periplus is at least as old as the earliest Greek historian, the Ionian Hecataeus of Miletus. The works of Herodotus and Thucydides contain passages that appear to have been based on peripli.
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1st century Greco-Roman periplus
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