peridioles

Peridioles are small, disc-shaped containers historically used to hold vellum or paper manuscripts, particularly in medieval Europe. They are most commonly associated with the codex known as the “troff” or “trecento” codex, where each peridiole contained a single text or illustration, often bound together with cords or cords and wooden pins within a larger protective case. The word derives from the Greek “peridion,” meaning “a small object surrounding something.”

The typical peridiole measures between 2 and 4 centimeters in diameter and is crafted from ivory, bone, wood, or hardened paste. The interior cavity is sealed with a wax or resin coating to protect the delicate contents from moisture and insects. Peridioles were frequently employed in the production of illuminated manuscripts, serving as modular units that could be replaced or rearranged without damaging the overarching volume. This modularity facilitated the dissemination of texts such as religious liturgies, astronomical tables, and medical treatises across monastic libraries.

In the 13th and 14th centuries, peridioles gained prominence in the production of “rebuses” and “mind‑maps,” where visual symbols inside the container complemented textual information. Their use declined with the advent of more efficient binding techniques in the Renaissance, although a few examples persisted in private collections and scholarly archives well into the 17th century.

Surviving peridioles are valuable to scholars for insights into medieval bookmaking, material culture, and the transmission of knowledge. Conservation efforts focus on stabilizing the fragile outer casings and preserving the original inks and pigments on the internal sheets. Notable collections are housed in the British Library, the Bibliothèque Nationale de France, and the Vatican Library.