Is there for honest Poverty That hings his head, and a'that; The coward-slave, we pass him by, We dare be poor for a'that! For a'that, and a'that, Our toils obscure, and a'that, The rank is but the guinea's stamp, The man's the gowd for a'that.

-Burns, Robert
  'For a' that and a' that', stanza1.

The force of theguineayou have inyour pocket depends wholly on the default of a guinea in your neighbour's pocket.If he did not want it, it would be of no usetoyou.

-Ruskin,John
  Unto this Last, essay 2.

But the jingling of the guinea helps the hurt that Honour feels.

-Tennyson
  Poems,'Locksley Hall', l.105.

We're all of us guinea pigs in the laboratory of God. Humanity is just a work in progress.

-Williams,TennesseeThomas Lanier
  The Gipsy. Camino Real, block12.