What mechanical solution was engineered in the early 16th century to combat the non-linear power output of the mainspring?

Answer

The fusee

The fusee, a specially shaped pulley system developed in the early part of the 16th century, worked with the mainspring barrel to equalize the transmission of power, converting the varying pull of the spring into a more uniform force.

What mechanical solution was engineered in the early 16th century to combat the non-linear power output of the mainspring?
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