Treasure Stone: you'll need 1 cup flour 1 cup used coffee grounds cup salt cup sand cup water. When doing a dinosaur study, I bought small plastic dinosaurs to insert and made dinosaur eggs. After several days we cracked the eggs open and voila!
1 Cardboard Marble Maze Cardboard Marble Maze: Here is a low tech visual perceptual marble maze made out of a cardboard box and some straws. This one is fairly simple, but it can be useful for those who have trouble with motor.