I sent a thread on this a couple of weeks ago when I saw the Jordon's Fabric video on Cutting Corners. Her husband uses an 8 pound weight. I thought it was a great idea and bought one. It works great. I got mine at Target for $5.49.
By the way, I bought their pre-cut blocks in green/blue and did it at the quilting treat. It was very easy and makes a striking quilt. I would post it, but I haven't a clue on how to get a picture on this website.