Definition of "cornish"

So the curve of Stonehenge, which is above 100 English feet, appears extraordinary large and well proportion'd, upon a height of 18 foot, which reaches to the top of the outer cornish; that of the inner cornishes is but 24 foot high, at a medium. For the cornishes of the inner part of Stonehenge, or that which Webb calls the cell, are not all of equal height, of which in proper place.

1730, William Stukeley, Stonehenge: A Temple Restor'd to the British Druids, page 11

The four rooms in the length of this building have door places crown'd with double cornishes, as represented in the plate of that architecture, together with ornaments of the winged globe.

1743, Richard Pococke, A Description of the East and Some Other Countries, page 63

And all the way along the edges here we'll be putting in cornishes. They're under the scaffolding there in the corner, you can take a look. These are six-inch cornishes.

2009, Ivan Vladislavic, Portrait with Keys: The City of Johannesburg Unlocked, page 114