Acknowledging the contribution of mathematicians to the mathematical education of teachers, we explore mathematicians' perspective on an envisioned Calculus course for prospective teachers. We analyzed semi-structured interviews with 24 mathematicians using the EDW (Essence-Doing-Worth) framework (Hoffmann & Even, 2018, 2019); and subsequently, we adapted the framework by extending and refining the existing themes. The findings of our study indicate that the mathematicians believe the primary purpose of a Calculus course for teachers is to communicate the nature of mathematics as a discipline. By providing a variety of examples that could shape and expand the teachers' understanding of mathematics, the majority of the mathematicians participating in the study emphasized the value of mathematical investigation in an envisioned Calculus course for teachers, as well as connections within and beyond the subject.