Matthew Battles: The visualization was coded in Processing by our former research fellow Travis Bost. We used Harvard library collections data made available through an API developed by the Library Innovation Lab, a group headed by David Weinberger in the Law Library. This API gave us access to library records, which we searched, downloaded, and cleaned up until we had what we thought was a reasonable representation of editions that actually were printed in early-modern Europe controlling for latter-day reprints, reissues, scholarly editions, and the like; we also sought to exclude Asian materials and items in manuscript.

via The Explosion of 15th Century Printing: A Data Visualization – Kasia Cieplak-Mayr von Baldegg – The Atlantic.