I use a digital fish weighing scale.  Weighs in oz/lbs or grams, has Tare
feature, was accurate according to my vets scale.  Costs around $30 at
Wal-Mart, find it in the sporting goods section.
 
Directions for use:
 
Turn on scale.
 
Place sleeping ferret in plastic bag with handles, hang bag on scale hook.
 
Record weight, keep a written record.
 
I say *sleeping* ferret because they think this is a wonderful play idea,
and trying to get a accurate weight on a bouncing, berserk ferret is not
an easy thing.
 
Ardith
Parris 2 lbs 9 oz
The Kidd 2 lbs 13 oz
The Little Kidd 2 lbs 2 oz and gaining
[Posted in FML issue 4403]