Under the maxim Ars corrigendi, it was discussed in the Early Modern period how authentic versions of texts could be extracted from ancient literature, as the texts in the manuscripts had been affected by many slips of the pen and other editorial revisions which they had endured on their long journey of tradition during the Middle Ages. The current study reconstructs instructions from the 16th century which demanded the corrector s knowledge of the history of writing and an appropriate method for the laborious work. Ars corrigendi is the fundamental technique with which the science was first able to obtain access to the exemplary sources, and therewith to the ancient world itself.