Homemade scales are easy if you can find something that weighs a known amount of grams. A simple scale:
Nail a thumb tack to the wall and put some heavy string in the middle. On the ends of the string tie two styrofoam cups. One cup is empty and the other has 10 pennies in it. On the bottom of the tack take a banner sheet and place it there. Where the bottom of the empty penny cup is make a mark, and that will be 0 grams. Then take a penny and place it in the empty cup and make a mark, and that will be 2.5 grams. One more penny would be 5 grams. Continue this process untill you reach 10 pennies in each cup. The limit of this scale is 25 grams and it won't be accurate (unless you're good at measurement), but it should work.

The things you think of when you're blazed.