Many thanks to Preston Stone, who did the majority of the hard work on this project and allowed me to share it.
A periplus 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. It 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.
This document is a Greco-Roman periplus written in Koine Greek that describes navigation and trading opportunities from Roman Egyptian ports like Berenice Troglodytica along the coast of the Red Sea, and others along Horn of Africa, the Sindh region of Pakistan, along with southwestern regions of India. The text has been ascribed to different dates between the first and third centuries, but a mid-first century date is now the most commonly accepted. While the author is unknown, it is clearly a firsthand description by someone familiar with the area and is nearly unique in providing accurate insights into what the ancient Hellenic world knew about the lands around the Indian Ocean.