It is always good to have a clear idea of how a book comes into our hands.
In 1562 Mattias Flacius, who was writing a church history in the Lutheran interest, happened upon a handwritten medieval book at Minden in Germany, which contained an ancient text previously unknown. The work was De errore profanum religionem (On the error of pagan religion) by Firmicus Maternus, and was dedicated to the emperors Constantius II and Constans.
Recognising an unpublished text, he sent it to Strasburg, where it was printed with his corrections and notes. Unfortunately he did his work so poorly that the text was unintelligible in parts. This was a problem, since the Minden manuscript disappeared soon after Flacius used it.
In 1603 Johannes Wouwer printed another edition at Froben, with his own emendations on the Flacius edition. This became the basis for study for the next two centuries, and various editions were based on this.
In 1856 Conrad Bursian determined from a catalogue that a manuscript must exist in the Vatican, in Ms. Palatinus Latinus 165. A collation was obtained and used.
The Vatican manuscript is now the only handwritten copy known to have survived the Dark Ages and the Middle Ages. It was written in Germany in the 9-10th centuries, and is mutiliated at the beginning.
It contains notes in the hand of Flacius, which shows that this is the “Minden” manuscript. The Palatine collection in the Vatican comes from Germany. It consists of manuscripts from the Rhineland Palatinate, from Heidelberg. Flacius himself may have removed the book from the monks of Minden — he removed books from Fulda — or the Elector Palatine may have done so. The collection was transferred to the Vatican at the end of the Thirty Years War. The book has lost some leaves after folio 4, including an important passage on Mithras.
These notes culled from the introduction to the Teubner text by Ziegler, available on Google books, 1905