Egg of Columbus
Egg of Columbus is an expression that means an unexpectedly easy way out of a difficult situation.
According to legend, when Christopher Columbus told Cardinal Mendoza about how he discovered land west of the Atlantic ocean, one of the people with them said, "What could be easier than to discover a new land?" To which Columbus offered him a simple task: to put the egg on the table and make it balance on its end. When none of the other people could do it, Columbus took the egg, smashed it from one end, and placed it on the table, showing that it was actually very simple. Seeing this, everyone began to object, saying that they could do the same. To which Columbus replied, "The difference, gentlemen, is that you could do it, when I did."
Historians are not sure if Columbus really did this in real life. They think it is likely that people made the story up many years later.
Girolamo Benzoni wrote about this story in Historia del Mondo Nuovo in 1565. Historians think Benzoni might have been the first person to tell the story, but they are not sure.
One reason they think so is that almost the exact same story showed up in another book, by painter Giorgio Vasari in 1550. In Vasari's book, it was the builder Filippo Brunelleschi who flattened the egg. This was to explain how he built the heavy done for the Santa Maria del Fiore church.
In English, people use term "egg of Columbus" to describe puzzles.