It's quite clearly the pound of British pounds. With a pound of feathers, one may feel a sense of 'freedom' as if they could attach the feathers to their bodies or clothes and fly away. A pound of British pounds carries the baggage of capitalism; the holder will not feel the sense of weightlessness, but rather the incessant need of more. You're gonna carry that weight.
I don't think you can buy many feathers for a pound, so probably the pound of pounds. I say probably because I'm not ruling out the possibility of buying a couple of feathers from like, an enormous bird.