Strabo Geography 2.5.16

[16] Such being the configuration of the whole earth, it will be convenient to take two straight lines, cutting each other at right angles, and running the one through its greatest length, and the other through its breadth. The former of these lines will represent one of the parallels, and the latter one of the meridians. ¹ Afterwards we must imagine other lines parallel to either of these respectively, and dividing both the land and sea with which we are acquainted. By this means the form of the habitable earth will appear more clearly to be such as we have described it; likewise the extent of the various lines, whether traced through its length or breadth, and the latitudes [of places], will also be more clearly distinguished, whether north or south, as also [the longitudes] whether east or west. However, these right lines should be drawn through places that are known. Two have already been thus fixed upon, I mean the two middle [lines] running through its length and breadth, which have been already explained, and by means of these the others may easily be determined. These lines will serve us as marks to distinguish countries situated under the same parallel, and otherwise to determine different positions both in respect to the other portions of the earth, and also of the celestial appearances.