German scientist Daniel Gottlieb Messerschmidt (1685-1735) - the first explorer of Siberia, traveled at the end of 1726 on the way from Siberia to St. Petersburg through the lands of the northern Udmurts (along the river Cheptsy) and provided in his diary information about the Udmurt traditional costume and dwelling, ethnonymy, folk religion, etc., and also compiled the first fairly voluminous (more than 300 words) dictionary of the Udmurt language in history. The materials of D. G. Messerschmidt, which thus represent the first scientific data on the Udmurts and the Udmurt language, accompanied by the necessary historical, ethnographic and linguistic comments, are first published in the proposed book.