A classic.

In Henri Charrière's masterpiece 'Papillon' (made into a film with Steve McQueen and Dustin Hoffman) the French convicts in a brutal penal colony on Devil's Island would keep cash in a cylindrical tube called a 'plan' up their bums, as the only safe storage.

Great movie, made more complicated when you realize it was written by Stalinist screenwriter Dalton Trumbo. I'm against the blacklist but it also reframes the final proclamations of McQueen's character as something other than freedom triumphing.