Weight, weight, don't tell me

We began our discussion of weight today, starting with the customary units -- ounces, pounds, and tons. The kids actually seemed to grasp the concept pretty well. They quickly came to realize that very light things should be measured with ounces, very heavy things with tons, and anything in between with pounds.

For some, it took a while to realize that even heavy things can be measured with pounds -- some kids for instance tried to list ME as something that would weigh a ton -- but they got it in the end.

Tomorrow we will discuss the metric units, gram and kilogram, and that always seems to be harder to grasp. The benchmark for a kilogram is always a baseball bat, but I think a lot of my kids don't really know how heavy a baseball bat is, and I don't have one at school. I've also seen a pineapple, but just today the book had an example of a pineapple weighing 5 pounds. 5 pounds is not a kilogram.

Any suggestions for what I can use to represent a kilogram? Maybe a textbook?