The link has been already provided above (opus cit), it's directly connected to the very question of gradients, providing a specific implementation (it even comes with a circuit diagram). As you were claiming a lack of detail (but apparently not honoring the provided citation)…
(The earlier you go back in the papers, the more specifics you will find.)
That claim was never made, but by you. The claim was, Minsky had practical experience and wrote about experiences with gradient descend (aka "hill climbing") and problems of locality in a paper published Jan. 1961.
On the other hand: who invented "hill climbing"? You've contributed nothing to the question, you've posed (which was never mine, nor even an implicit part of any claims made).
(The earlier you go back in the papers, the more specifics you will find.)