How to make such sofa?

 From:  Frenchy Pilou (PILOU)
You must have the drawing section of the seam: here a very tiny ellipse
make a Sweep seam along the lines
boolean diff between cube and the Sweep ;)
Then fillet the Edges
But not sure that Nurbs are for this nature of object but maybe I miss something :)

EDITED: 12 Dec 2011 by PILOU