" When the pies were taken out of the oven, melted fat was poured in through a hole in the lid to exclude air, thus preserving the contents. Once the pie was cut this airtight seal was broken, leaving the contents prone to rapid spoilage - which perhaps gave rise to the old superstition that it is unlucky to take just one slice from a pie. "

― Janet Clarkson, , Pie: A Global History