What mechanism did Watt invent to convert the piston's reciprocating motion into continuous rotary power?

Answer

The sun and planet gear mechanism, or later, the crank and flywheel system

To move beyond simple pumping and drive factory machinery like looms and lathes, Watt invented mechanisms to convert the up-and-down motion into continuous rotary motion.

What mechanism did Watt invent to convert the piston's reciprocating motion into continuous rotary power?
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