  A simple n-gon is a polygon with n edges such that each vertex belongs to
exactly two edges and every other point belongs to at most one edge. Brass,
Moser and Pach asked the following question: For n > 3 odd, what is the maximum
perimeter of a simple n-gon contained in a Euclidean unit disk? In 2009, Audet,
Hansen and Messine answered this question, and showed that the supremum is the
perimeter of an isosceles triangle inscribed in the disk, with an edge of
multiplicity n-2. L\'angi generalized their result for polygons contained in a
hyperbolic disk. In this note we find the supremum of the perimeters of simple
n-gons contained in an arbitrary plane convex body in the Euclidean or in the
hyperbolic plane.
