Imbucare box with triangular prism

Imbucare Box With Triangular Prism sets the child one clear task: to bring the prism into the opening made for it. The triangle passes only in one position, so the child turns it in the hand until the shape matches, and then the piece disappears and comes back again. Wrist and eye work together here in a way a ball never asks for, since a rolling shape drops in at any angle while a prism has to be lined up first. That quiet return is the child's proof that things go on existing out of sight. For children under three.