A corpus of 360 distinct early modern printed editions (from 1472 to 1650) containing Johannes de Sacrobosco’s Tractatus de sphaera is “dissected” into a corpus of 540 text-parts, 241 of them re-occurring at least once. Through the exploration of the data, we recognized a relevant position for four anonymous authors in their social network. We demonstrate that the text-parts originally assigned to the anonymous authors were authored or edited by Georg Rheticus. By means of data analysis, we conclusively establish that Rheticus profoundly impacted the content of such textbooks for the introductory class in geocentric astronomy all over Europe between 1538 and 1629.