It measures 1.5cm in the narrower part of the nose, 2.5cm in the middle part of the saddle where the nose turns into seat, and 3.5cm where the seat is the widest. It is a little wider still at the very back end of the saddle, but I figure that part's not too useful as far as cutouts go...
The Selle Italia website has good photos of it- but don't forget to look under "offroad" saddles.