The article is an excerpt from the biography of the Russian writer, historian and collector of curiosities F. Dmitriev-Mamonov, to be published by B.S.G.-Press. The fragment considers three hitherto undisclosed episodes of his life: the 1770 criminal investigation of Mamonov’s attempted poisoning by the writer and former lecturer of the Land Gentry Cadet Corps Johann Fonberg, who had worked as his personal librarian for two months; followed by problems with his mental health in the 1780s, when he began suspecting that his closest family were plotting to kill him and began to subject his serfs to harsh punishments; and, finally, his donations to Moscow University in May 1770, in February 1772 and, probably, in November 1779, which consisted of a collection of medals, copies of P. Lippert’s engraved gems, and the portrait of field marshal P. Saltykov. All three instances appear connected: the donations coincide with three major incidents in Mamonov’s life (the attempted poisoning, a bad wound sustained in Chudov monastery during the suppression of the Plague revolt, and official proceedings against him for cruel treatment of serfs), which forced him to contemplate his mortality and the need to plan for the future of his collection.