pie, putting his thumb in

an allusion to the nursery rhyme "Little Jack Horner," a tale of the dishonest dealings in the days of King Henry VIII of England (1509-1547) where a man by the name of John Horner, a steward of Glastonbury (town in southwest England) was sent to London with a pie for the king. Title deeds for several estates were baked into the pie. The greedy Horner stuck his thumb into the pie before he got to London, in other words, he stole the Kings deeds. Papers were often baked in pies at this time. It was a favorite trick in the 1500s to hide surprises of all kinds in pies.