Gerard Mercator’s edition of Ptolemy’s ‘Geography’ is highly acclaimed; he spent much of his life studying the work and even engraved the plates himself. The ‘Geographia’ is the earliest surviving geographical treatise. Much of Mercator’s efforts were spent projecting Ptolemy’s geography onto the projection which bears his name. Mercator is one of the world’s greatest cartographers and the ‘Claudii Ptolemaei Tabulae Geographicae Orbis Terrarum’ was first published in 1578. This map shows the northern half of Africa with the equator displayed prominently is in the third state with the addition of a latitude and longitude grid illustrating the projection. The source of the Nile River is also highlighted. Koeman Me 5; Nordenskiold 234; Phillips, P.L. (Atlases) 384; Shirley BL T.Ptol-11a & 11k; Van der Krogt, P. (Atlantes) 1:501.