  We give a categorical formulation of Kraus' "magic trick" for recovering
information from truncated types. Rather than type theory, we work in Van den
Berg-Moerdijk path categories with a univalent universe, and rather than
propositional truncation we work with arbitrary cofibrations, which includes
truncation as a special case. We show, using Kraus' argument that any
cofibration with homogeneous domain is a monomorphism. We give some simple
concrete examples in groupoids to illustrate the interaction between
homogeneous types, cofibrations and univalent fibrations.
