Building canals, fountains, bridges, and aqueducts was one of the main duties of the architects in the early modern Ottoman world. However, the intellectual and practical tools of architects during the construction and repair of water systems have been rarely examined. Sinan’s texts underscore the inherent link between reason, intuition, bodily memory, ancient ruins, and geometrical knowledge during the embodiment of waterworks in Istanbul. In this paper, I will discuss this relationship against the backdrop of Cafer Efendi’s definitions of geometry and mason’s calculation in his book on architecture (Risāle-i Mi’māriyye, c.1614). Moreover, I will demonstrate that Cafer’s reference to the measurement and proportioning of canals sheds light on the only drawing that was attributed to Mimar Sinan, which is a schematic map of the Kırkçeşme water supply system. In addition, Eyyubi’s poems on aqueducts in Istanbul, which convey the repairs and emphasize the importance of firm foundations against natural catastrophes, reveal crucial points regarding the organization and maintenance of building sites. I argue that dexterity, geometrical knowledge, and innate talent appear side by side in such primary sources and demonstrate the fluid boundaries between these notions within the context of early modern Ottoman building practices.