The Introduction to Einblicke in die Coss von Adam Ries states:-
In addition to his famous arithmetic primers Adam Ries has also written an extensive algebra book: The Coss. The symbol for the unknown, or variable, was called 'coss' in the middle ages. Adam Ries also called it radix, root or thing. Ries's Coss, which, contrary to contemporary custom, was not written in Latin, but in German, is a link between the medieval descriptive algebra and the analytical algebra of modern days. However, Adam Ries did not succeed in publishing the manuscript of his Coss. The original manuscript was thought to be missing for a long time and is now stored in the Erzgebirge Museum of Annaberg-Buchholz. The objective of this edition is to make Adam Ries's Coss accessible to a broad readership and to encourage efforts for its restoration.
The selection provides glimpses into the hand-written original of the Coss, accompanied by parallel transliterated passages. This permits the reader to make comparisons. Scientific contributions and commentary provide information on the history and the significance of the word 'coss'. In addition to a short biographical outline there are also some remarks on the well-known arithmetic primers of Adam Ries and their relationship to the Coss.
The selections are taken from Coss 1, Coss 2, and the "Data" of Jordanus Nemorarius. The collection concludes with the following commentaries: The history of the Coss (Peter Rochhaus); On the significance of the Coss of Adam Ries (Wolfgang Kaunzner); The arithmetic primers of Adam Ries (Manfred Weidauer); Biographical miscellanea on Adam Ries (Hans Wussing).