Which preposition to use with impracticability

of Occurrences 33%

He pleaded the probable utter impracticability of such an enterprise.

in Occurrences 1%

But there was a degree of impracticability in these ladies, which, if it was unfortunate, was, nevertheless, a part of their Creole beauty, and made the absence of any really brilliant outlook what the galaxy makes a moonless sky.

Which preposition to use with  impracticability