This paper presents a study of instructors' and students' perceptions of the knowledge to be learned about limits of functions in a college level Calculus course, taught in a North American college institution. I modeled these perceptions using a theoretical framework that combines elements of the Anthropological Theory of the Didactic, developed in mathematics education, with a framework for the study of institutions developed in political science. While a model of the instructors' perceptions could be formulated mostly in mathematical terms, a model of the students' perceptions included an eclectic mixture of mathematical, social, cognitive, and didactic norms. I describe the models and illustrate them with examples from the empirical data on which they have been built.