What do you use as a dense counterweight?

I am making a wooden paper towel holder and I want to insert some sort of counterweight into the base (hidden so that it is out of sight) so that the holder is much heavier.

I don't know what product to use as this counterweight and where to find it.

Submitted August 10, 2016 at 02:51PM by bellep http://ift.tt/2aLHvL9