Written about in the early 13th century by the poet, chronicler and physician Peter of Eboli, the didactic poem, De balneis Putelolanis (The baths of Pozzuoli) was the first widely distributed medieval guidebook to medicinal baths, of which there were 35 in the Pozzuoli region, near Naples. Of copies made from the 13th to 15th centuries, 20 survived, 10 of which were illuminated, each with one miniature for each of the 35 baths described. These are the only surviving examples of medieval secular book illumination on a subject of predominantly local interest as opposed to herbals or romances. The facsimile edition cited is of the 13th century copy in the Bibliotheca Angelica, Rome. Digital facsimile of a 15th century illuminated manuscript of the text from Roderic.uv.es at this link. Digital facsimile of a 14th century manuscript from the Fondation Martin Bodmer at this link.