TThis article is devoted to exposing and considering the most unique and interesting book monuments stored in the collections of the Central Scientific Library named after Yakub Kolas of the National Academy of Sciences of Belarus. It reveals the features of some copies of the French philosopher and naturalist Rene Descartes’ works dated to the XVII–XX centuries. The main part of the research is based on studying the traces of existence of individual copies from the National Library of the National Academy of Sciences of Belarus, including the lifetime edition of Rene Descartes "Discours sur la method". The description of these copies’ specific features (stamps, records, marks of previous owners) is presented.This study aim consists in demonstrating the need to identify rare and valuable monuments of book culture stored in libraries and often hidden from the employees themselves. The methods used in the study are that of heuristic search and attribution of copies of book culture. The article reflects one of the most relevant and productive areas of research work in academic libraries: that is search, identification and scientific description of book monuments stored in their collections, and their presentation in electronic repositories. The identification of 14 works by Rene Descartes and the description of the most interesting of them has become the result of the study. The material is interesting for library specialists working with rare and ancient documents and engaged in the study and popularization of library collections.