Frédéric Cailliaud ran the Natural History Museum of Nantes from 1836 to 1869. An explorer, Egyptologist, geologist, and public political figure, Cailliaud’s profile resists any attempt at categorization, yet a common denominator of his activities is the production of knowledge about nature. As an employee of the Nantes municipality, Cailliaud’s activities, especially fieldwork, intersected with administrative demands. This did not make him the puppet of standardizing bureaucratic forces. Rather, the term bureaucracy is used in this article as an epistemic category to reassess the role of instrumental changes in scientific knowledge production as it was increasingly integrated into public administration. Focusing on Cailliaud’s papers (notes, manuscripts, publications) and the place of fieldwork in them, this article seeks to cast light on the material and relational dimensions of knowledge production in a nineteenth-century provincial museum. In doing so, I seek to reassess the place of bureaucratic work in the production of geological knowledge and argue that the field and the office were not “separate worlds.” Instead, the exploration of their entanglements complexifies our understanding of knowledge production in the nineteenth century.