This article focuses on the lavishly decorated Calderini Pontifical (Houghton Library, Harvard University, MS Typ 1), which gets its name from an inscription and the heraldry of Andrea Calderini from Bologna – hitherto erroneously assumed to be the bishop of Ceneda in 1378-1385 – who held that episcopal see in the third quarter of the 15th century.
Heraldic and iconographic evidence prove that the Pontifical was originally intended for the chapel of Pope Innocent VII Migliorati (1404-1406). Having remained unfinished, the decoration of the manuscript was completed by the Florentine illuminator Bartolomeo Varnucci at the expense of Andrea Calderini. Consequently, the papal triregnum and escutcheons were covered up with the coat of arms of the bishop of Ceneda. This conclusion allows us to rearrange the dating of the entire career of the outstanding calligrapher Stephanus de Aquila – documented in the papal chancery from 1380 to 1407 – who is partly credited with the magnificent pen-work repertoire of the first phase of the Pontifical. On this occasion he was accompanied by an illuminator from Abruzzo who can be identified as the author of the decoration of f. 2r in the first volume of a Gradual from the church of Santa Maria Paganica in L'Aquila (1382-1385). After being trained in the tradition of manuscript illumination that flourished in Teramo in the 14th century, this anonymous master enriched his repertoire with the stylistic motifs of Bolognese illumination before moving to Rome during the years of the Great Schism, where other scribes and illuminators from the Abruzzi were working in the papal chancery. Among them, the celebrated ars nova composer Zacara da Teramo – active as a scribe and miniaturist – may be considered to be the person responsible for the illumination of the Pontifical..