All you need are paper clips ... lots and lots of paper clips of the same size. Did I mention you need paper clips? I think you get the point.
I gave my son a worksheet I'd cooked up to get him started. While I don't want to overwhelm my son with worksheets, I do like that they sneak in extra reading practice and help me gauge how well he does following directions. (Download the worksheet I made here.)
the chair he was sitting in,
and his pencil.
After measuring these (plus his foot and a book) he needed to review the number of paper clips each required and put them in order from greatest to least.
Stringing paper clips was a bit of a struggle for my son at first but, with some serious concentration and a whole heap of determination, he caught on.
We'll be doing this activity again, I'm sure!