'A called-for falling glide and whirl'

 I have rather too much going on at the moment, including some soul-sapping technical difficulties resulting from a change of computer, and a couple of books to read for review at something of a breakneck speed (for me) – but, on the positive side, I did manage an epic day trip down to the south coast and back yesterday to see an old friend who also happens to have a magical ability to fix bad backs, of which I have had one, in a small way, lately.  
  Anyhow (a word Siegfried Sassoon uses surprisingly often in The Old Century at the beginning of paragraphs), somewhere along the way I came across this short poem by Richard Wilbur (from Things of This World), a vivid miniature that struck me as, well, just beautiful...

Piazza di Spagna, Early Morning

            I can't forget
   How she stood at the top of that long marble stair
   Amazed, and then with a sleepy pirouette
Went dancing slowly down to the fountain-quieted square;

          Nothing upon her face
But some impersonal loneliness, – not then a girl,
    But as it were a reverie of the place,
       A called-for falling glide and whirl;

   As when a leaf, petal, or thin chip
Is drawn to the falls of a pool and, circling a moment above it,
           Rides on over the lip – 
     Perfectly beautiful, perfectly ignorant of it. 

To me, the image in that last stanza recalls Wilbur's masterpiece, 'A Baroque Wall Fountain in the Villa Sciarra'.