The half-redacted sphere of Pythagoras.
Over the passage of decades, layers of meaning and controversy can gather in manuscripts like accumulated seasons of fallen autumn leaves. At some point in the ninth century, a scribe in the Abbaye de Saint-Amand in the Foret de Vicoigne in far northern France copied a creed ascribed to St. Ambrose in tiny Carolingian minuscule on what is now Pal.lat.176 fol.162v (which has parallels in the Codex Muratorianus in Milan, fol.73v), but left a wide expanse of empty parchment below. At some point, the manuscript passed to the Abbey and Altenmünster at Lorsch, in the Bergstraße district of Hesse, and an opportunistic scribe used a later, thorny, script to complete a Sphaera Pythagoras in the vacant space.
There are many such iatromathematical devices in medieval manuscripts, and were used for simple prognostication. If a fellow monk fell ill, the idea was to assign the Roman numerals in the column to the left with the respective letters of his name, add them together with the day of the synodic month on which the illness first occurred and the day of the week, and divide by 30. If the remainder is in the upper half of the crossbones, the patient will live; if below, they will either perish quickly or linger in sickness until consumed by death. Really, the thing reminds me of nothing more than the origami paper ‘cootie-catchers’ we used to make in elementary school. But apparently, it meant something much more serious to a third monk, who wrote anathema above, and quickly crossed out the column, x-y axis of the disc, and instructions with quick strokes of red ink. I assume the heresy was not quite enough to deserve more than a hasty redaction, for despite the warning, the sphere can be easily read.