Dry 40 year old Foam?
 

I was getting ready to remove 500 pounds of wet foam, but I couldn't find it. WTF? I knew it was wet, because when I stand on it, I see water squeeze out. So imagine my surprise when I chopped a big hunk out with a cold chisel and it was dry???and feather-lite??? Maybe the water is at the bottom? So I cut it all the way through.....dry! Guess I'll leave it, but what will I do with all of the extra time and money?

"but what will I do with all of the extra time and money?"

Send the money to me!! :) You can keep the time for yourself.