'Fishing for Elephants'

From Henry Nelson Coleridge's The Literary Remains of Samuel Taylor Coleridge (2 vols, 1836), 1:148:

Speaking of the small German potentates, I dictated the phrase—officious for equivalents. This my amanuensis wrote—fishing for elephants;—which, as I observed at the time, was a sort of Noah's angling, that could hardly have occurred, except at the commencement of the Deluge.

It's an expressive phrase, especially in the context of Coleridge and his lifelong attempts to snare in the tendrils of his tangling prose some very large truths indeed. Why fish for minnows when we can fish for elephants? Truth, genius, God. It's the elephant in the Rhine.

One wrinkle: I can't find anywhere in Coleridge's works where he refers to German potentates, or anybody else, being officious for equivalents. Might he simply have made this rather delicious mis-hearing up? It wouldn't be the first time he did such a thing.

The 'elephant in the Rhine' line was bad, I admit it. But originally I was going to go with an 'it's the elephant in the Rhûn' gag, so you can count yourselves lucky.