What is the most popular puzzle?

What is the most popular puzzle? In 1974, Hungarian architect Ernő Rubik created his eponymous Cube as a teaching tool for his students. His students loved playing with the Cube which inspired him to make it more widely available. Forty years on, the Cube has sold 350 million copies making it the most popular puzzle of all time.

In 1974, Hungarian architect Ernő Rubik created his eponymous Cube as a teaching tool for his students. His students loved playing with the Cube which inspired him to make it more widely available. Forty years on, the Cube has sold 350 million copies making it the most popular puzzle of all time.