This article focuses on an epistle written in the vernacular by the poet Simone Serdini da Siena il Saviozzo and transmitted in Cod. 2649 of the Österreichische Nationalbibliothek in Vienna. The study includes a critical edition and analysis of the text, which has heretofore been all but completely neglected in scholarly research. From the epistle, we learn of the existence of an unknown manuscript ‘edition’ of Rerum vulgarium fragmenta (RVF), one that was compiled by Saviozzo himself in 1409 and dedicated to Domenico Bettini, referendarius domini to Pandolfo III Malatesta. The article contextualizes his endeavour to spread Petrarch’s work amongst the cultural milieu of the Malatesta court in Brescia, as well as his previous activity as editor of Dante’s works. It then goes on to define Saviozzo’s knowledge and interpretation of Petrarch presented in the brief accessus ad auctorem of the epistle. Lastly, it establishes which branch of the RVF manuscript tradition derived from this operation, delving further into a ‘form’ of the Canzoniere that is clearly of utmost interest.