It has been long assumed that Mendel’s statistical knowledge at least partially originated from his interest and studies in meteorology. While some of his textbooks he used for study are known, others remained unidentified and its has remained also not possible so far to date some of the handwritten notes that Mendel left in his textbooks. We here provide a first dating of Mendel’s notes in his physics textbook of August Kunzek and identify the remaining unidentified textbook that he had used for his first homework on meteorology.