This article is devoted to a diplomatic (formal) analysis of 13 documents, including 12 originals issued by Russian tsars between 1576 and 1707, which are kept at the Kórnik Library. Among them, there are two original letters by Tsar Michael of Russia dating to 1634 and 1645 and four documents by Tsar Alexis of Russia from 1645 and 1668–1669. The collection also includes Peter the Great’s mandate of 1707 given to Russian negotiators for talks with representatives of the Sandomierz confederation, two extremely interesting documents (in the form of scrolls) of border-related negotiations dating to 1634 and 1645, as well as a notebook of 40 pages containing the Russian party’s proposals presented to Polish envoys during negotiations in Moscow at the turn of 1671 and 1672. The article is enriched with an analysis of the content of four well-preserved tsar’s seals applied to the documents in question.

The holdings of the Kórnik Library include a book of abstracts of lawsuits concerning the boundaries of estates in Greater Poland in the 15th–17th century, written in Latin. Its presumed author, the otherwise unknown Piotr Biernacki, had the ability to write in both the Latin and the Cyrillic alphabet. This article focuses on the reading and the palaeographic and linguistic analysis of several Latin sentences, one heading and more than 20 margin notes written in the Cyrillic alphabet. The Cyrillic handwriting found in the book is a Russian skoropis used in Ukrainian areas of Poland in the 17th century. When writing the Latin text with the Cyrillic alphabet, the author utilised the Polish language of the time in the reading of Latin. The cryptograms found in the book have a technical/informative nature and do not contribute any significant information to the text. In combination with the fact that the Cyrillic alphabet was not at all used in Greater Poland, the above suggests that the author was playing with the reader, who was thus forced to look for the meaning of the incomprehensible text.