In response to quantum mechanics, so the story goes, Einstein proposed a machine, that, based on the uncertainty principle, was a perpetual motion. This showed that quantum mechanics was at odds with evidence that energy is conserved. Bohr later showed that the analysis was flawed; Einstein had failed to take gravity into account (ironically).

Is this story true? If so, what was the machine Einstein proposed, how was it supposed to work, and what did Bohr reveal about it?