The earliest record of a requirement for ships to carry lights that the author has been able to find is in the Rhodian Laws. These appear to date from about the 3rd or 2nd century B.C., and were certainly incorporated into Roman Law by A.D. 161, although Ashburner suggests that the earliest known copy dates from Byzantine times, A.D. 600–800. The Laws contain a section intended to prevent collisions between vessels under way and vessels at anchor or stopped.