So maybe this isn't an obvious tactic, and maybe large packages coming into a prison are searched more thoroughly than large packages leaving a prison -- but you'd expect prison guards to pay attention to anything large enough for a person to fit into. At the end of his shift, the inmate climbed into a cardboard box and was taken out of prison by express courier. His whereabouts are still unknown. I am remembering the tour of Alcatraz I took some years ago, and I think the tour guide talked about someone who tried to escape in a laundry cart. So maybe this isn't such a new idea after all.