  We previously proposed that entanglement across a planar surface can be
obtained from the partition function on a Euclidean hourglass geometry. Here we
extend the prescription to spherical entangling surfaces in conformal field
theory. We use the prescription to evaluate log terms in the entropy of a CFT
in two dimensions, a conformally-coupled scalar in four dimensions, and a
Maxwell field in four dimensions. For Maxwell we reproduce the extractable
entropy obtained by Soni and Trivedi. We take this as evidence that the
hourglass prescription provides a Euclidean technique for evaluating
extractable entropy in quantum field theory.
