Help - Dune quote

I need help recalling a sentence from Dune (first book) - it is too fragmented to Google I think.

It is something to do with a particular element limiting a system - if particular elements are nessacery, then the scarcest element acts as the limitation.

Can’t remember more than that - it is nice and pithy in the book.

Any questions please ask, I know this is obscure.

Hydraulic despotism? Hydraulic empire - Wikipedia

the Wiki is different than the Herbert quote, Frank used it as an example in one of the dune books though. I believe he was talking about electricity and how so many people relied on it that the government could kill millions simply by turning it off.

Kynes is probing Jessica’s knowledge of ecology at the dinner party that immediatley proceeds the Harkonnen invasion, she gets it right by describing the law of the minimum.

“It’s a rule of ecology,” Kynes said, “that the young Master appears to understand quite well. The struggle between life elements is the struggle for the free energy of a system”

The hydraulic despotism portion is from God Emperor of Dune.

I think that is it.

Thanks.