Bert and Ernie - "Fill it with" What?

[Mo Frackle]

From one of the Sesame albums. Does anyone know what Bert's saying at 1:10? It's repeated at 1:58.

"So, go ask a grown up for a soup can. Fill it with _____________________ kind of stone."

 

[sesamemuppetfan]

"Rattly" I think.