Williams said:

To make two bold statements: There's nothing sentimental about a machine, and: A poem is a small (or large) machine made out of words. When I say there's nothing sentimental about a poem, I mean that there can be no part that is redundant.

Prose may carry a load of ill-defined matter like a ship. But poetry is a machine which drives it, pruned to a perfect economy. As in all machines, its movement is intrinsic, undulant, a physical more than a literary character.

From: Williams's introduction to The Wedge, in Selected Essays of William Carlos Williams (NY: New Directions, 1969), p. 256.