 Ewen A. Whitaker argues that this likely refers to Mare Imbrium, "the largest regular-shaped dark area unbroken by bright patches" that can be seen with the naked eye.Around 1600, William Gilbert made a map of the Moon that names Mare Imbrium "Regio Magna Orientalis" (the Large Eastern Region).Michael van Langren's 1645 map named it "Mare Austriacum" (the Austrian Sea).