Historical maps are a major tool for the study of the logistics of the past. On their basis we make calculations and offer reconstructions. Yet such maps are modern maps in reality. We superimpose on them data derived from our sources. Based on state-of-the-art geography, they contain a wealth of accurate information about distances, elevations, terrain, river courses, coastal configurations, and much more, that the people we are studying simply did not possess. Consequently, reliance on them may mislead us into ascribing to these people logistical and other calculations they would not have been able to generate themselves.