In November 1689, a brief Tuscan encounter between Leibniz and Galileo’s last disciple Vincenzio Viviani set the stage for the epistemological confrontation of a symbolic ‘blind thought’ and the Florentine visual culture. Arguing about many problems of mechanics, hydraulics, and geometry stemming from Galileo’s intellectual as well as material heritage, the scholars shared two very different perspectives on the intricacies of a nascent physicomathematics at the crossroad of natural philosophy, mixed mathematics, and mechanical arts. In order to better understand the cultural peculiarities at the root of such a conflict of sensibilities, the present dissertation proposes to unveil the many networks of writings – scrips and drafts, scribbles and working papers, correspondences, and reading notes – underlying the published printed works of both savants. Delving into their personal archives and focusing on the materiality of working notes conceived of as paper tools, it becomes possible to shed light on the making of theory by tracing the multifarious material practices underpinning any intellectual operation. Words that do not form sentences, sentences that do not form texts, crossing-outs, symbols, figures, drawings, and schematics bear witness of a mindful hand and a handy mind jointly elaborating worlds on paper. Building on a hermeneutics of such handwritten inscriptions scattered on these early-modern folios, this archaeology of Viviani and Leibniz’s paper minds will question the long-inherited dichotomy between épistémè and tekhnè by unravelling the practice-ladenness of physico-mathematical theorizing. While underlining the similarities and discrepancies in the cognitive practices lying at the foundations of two forms of thought, this material history of savant work seen through the working papers of Viviani and Leibniz eventually understands knowledge as a production of meaning: a dynamical process woven from archival science, authorial strategies, rhetorical arguments, inscriptions making, drawings, and symbolics.