The Mysterious Statuary

So: I'm making an edition of Coleridge's Lectures on Shakespeare and part of that involves tracking down hitherto unidentified quotations and allusions, explaining references and so on. Foakes's edition does a pretty good job with the notes, actually, although there are about a dozen references that he can't nail. Of those I think I've identified the sources of all but two. The one that bugs me the most is this one, from the fourth lecture of the 1811-12 series. 'Statuary', in this passage, of course means 'sculptor':

There is said to be a statuary in ancient Greece whose figures were awkward and unideal in every respect but one—he had gained much praise from the beautiful feet and ancles of Venus. His name was introduced in a company of which his wife formed a part, and with as much delicacy as possible the merits of the husband were discussed. One person dwelt with much warmth of praise on the symmetry and grace of the feet and ancles of the Venus he had just completed. The wife was so transported at the compliment that she interrupted the eulogist by observing that her husband always took her for his model and she was always reckoned to have a most beautiful foot and ancle.

Gotta love that Regency spelling of 'ankle'. OK, so STC's point is straightforward enough: he is arguing that a true poet (or artist, or sculptor) must do more than merely 'copy' things to be great. But I cannot for the life of me find the source for Coleridge's anecdote here. Anybody know?