As a stave, there is too much wood there to register any minute weight lose. If you want to weight it, get a 5# or a 2# scale that weighs things in ounces. Reduce the stave to a bow blank, and then weight it. As the bow dries, the weight loss will show up on that scale. As it dries though, it may stay at a certain weight for a few days, and then start losing wight again. When the stave has lost no weight for 1/3 of the time it's been drying, then it's dry.