Through a close scrutiny of a set of manuscript notebooks by naturalists and scientific travelers such as Aimé Bonpland, Leopold von Buch, LJ Gay-Lussac, Alexander von Humboldt, André Michaux, Horace-Benedict de Saussure, and Dominique Villars, this study explored the gestures and cognitive practices at work in the routine writing of a scientific traveler’s journal. Two main sets of questions were investigated: first, the recording process itself, which explored the relationship between paying attention ("taking note") and recording ("taking notes"); and second, the uses of notebooks and their role in the production and construction of scientific knowledge, which show the scientific observer using notes as a kind of camera obscura, at once a reduction and a substitute for the world.