There are several types of puffball – are you sure they’re all edible?
See Wiki http://en.wikipedia.org/wiki/Puffball
“While most puffballs are not poisonous, some often look similar to young agarics, especially the deadly Amanitas, such as the death cap or destroying angel mushrooms. It is for this reason that all puffballs gathered in mushroom hunting should be cut in half lengthwise. Young puffballs in the edible stage, before maturation of the gleba, have undifferentiated white flesh within; whereas the gills of immature Amanita mushrooms can be seen if they are closely examined”
I used to really enjoy picking and eating wild puffballs until one day I foolishly included a puffball that had gone past the edible stage (the flesh was no longer white). I have never been so sick in my entire life, rivers of it coming out of both ends at once along with a raging fever. Even when I thought I’d got over it and went back to work, it suddenly attacked me and I nearly passed out in the loo whilst throwing up. For several years afterwards I only had to look at a mushroom and I felt queasy (I’d avoid them in the supermarket).
So, BE CAREFUL OUT THERE 8)