He was learning the sheep-keeping business, so as to follow on at the flock when the other should die, but had got no further than the rudiments as yet—still finding an insuperable difficulty in distinguishing between doing a thing well enough and doing it too well.
There are no more uses of "insuperable" in the book.
Show samples from other sources
This objection would be insuperable if Homer had been an Ithakan.
Homer -- The Odyssey
I came to the conclusion that difficulties, well-nigh insuperable, lay between me and the safe possession of the beautiful little vessel.