Click on picture for next
Here's everything you need.
From left to right:
1) A camera with a lens small enough to about fit in the opening of a milk jug. One with a macro focus mode is preferred.
2) An empty milk jug. Doesn't have to be from milk, just this kind of translucent plastic. You can use a gallon jug if you prefer.
3) Some way to measure things.
4) Optional - GooGone is a great way to get labels off very cleanly. For this you probably won't need to remove the label but now you know.