Last night I started The Visual Display of Quantitative Information by Edward Tufte, which is excellent. If you haven’t read it you may know it as the book featuring what I call the ‘Napoleon Graph‘, which Tufte calls the ‘best statistical graph ever drawn.’
But another graph featured in the book is even more interesting. It’s a tenth, possibly eleventh-century, depiction of the movement of the planets across the zodiac over time, and comes from a commentary on astronomy. The graph was included in an appendix added by an unknown transcriber of the main work. It’s not accurate at all—among many problems is the fact that the horizontal axis of any one planet can’t be reconciled with the others—but it was probably intended as a simple schematic for teaching purposes.
What’s really unusual here is that the graph has no known predecessor, and seems to have sprung purely from the imagination of it’s creator. Medieval writers and artists very rarely deviated from tradition. Most images, whether of scientific, medical, fictional, or religious subjects, were part of traditional illustrative cycles that had existed since the late classical period. There was some room for individual artists to maneuver within these tropes, but it was rare for something to appear completely out of the blue.
Not only is the graph unique, but it’s conceptually eight hundred years ahead of its time. According to Tufte, time-series charts didn’t appear again until the late eighteenth century, when academics and designers began experimenting with a variety of quantitative displays. And H. Gray Funkhouser, author of ‘A Note on a Tenth Century Graph’ in Osiris (vol. 1, Jan 1936) notes that the use of grids was uncommon even into the 1850s.