Ask Lemmygrad

Am I going crazy or something? Because I distinctly remember reading somewhere that the labor-power of a human, their capacity to perform labor is the economic analogue of the horse-power of an engine, it's ability to do work.

I also remember reading somewhere that Marx modeled the concept of labor-power after it's thermodynamic counterpart (hence the name, labor-power)

Now I've been searching for a source from Marx's own writings, and although the way marx treats labor-power is entirely analogous to how one might treat an engine with the capacity to do work, I haven't yet found an explicit comparison in his writings. Reading through chapters of capital is taking some time ...

So my question to the comrades here is, am I hallucinating this connection between political economy and thermodynamics, or is it real (and where in marx's writings should I look).

For additional context: I was banned from a certain place for using this analogy (oddly harsh punishment perhaps). I don't really care about being unbanned, but I do want to know if I was wrong.