[INCUNABLES]. DURANTI, Guillelmus [a. k. a. DURANDUS, William or DURAND, Guillaume, ca. 1237-1296]. Rationale Divinorum Offiiciorum... Strassburg: [Johan Pruss,] 1486. Folio. [3], 272, [1] ff. Complete with final blank. Text in double columns, rubricated throughout including a 6-line initial letter with a page-long flourish on a4 (folio 1). Contemporary blindtooled pigskin over oak boards. EARLY INCUNABLE EDITION OF THE MOST IMPORTANT MEDIEVAL TREATISE ON THE SYMBOLISM OF CHURCH ARCHITECTURE. AND RITUALS OF WORSHIP. 

First published in 1459, this is Duranti's most famous work, originally published by Fust and Schoeffer at Mainz. It was reprinted at least 40 times before 1500. "Its eight books contain a detailed account of the laws, ceremonies, customs, and mystical interpretation of the Roman Rite... [the] Rationale is the most complete medieval treatise of its kind; it is still the standard authority for the ritual of the thirteenth century and for the symbolism of rites and vestments..." (Catholic Encyclopedia). 

Binding a bit soiled, spine with old white paint, lacking fore-edge ties, two-line title with old inscriptions of a Salzburg cloister (the Convent of St. Peter and of "Domus S. Missionis Benedictinae Schwarzachii."). Two leaves with a few lines censored with ink on folios 245 and 249. A few gutters starting or cracking with some minor associated tears to text, light occasional dampstaining to text at upper margins. Some occasional contemporary maginalia. Still, a fine copy with large margins.