The Frozen River

A caravan needed to cross a frozen river. They tested the ice. Too thin.

They tried again an hour later. Still too thin.

The caravan master said: "Each time we test, we weaken the ice at that spot. And each hour, the cold strengthens it. If we test too often, we undermine the very thing we're waiting for."

They tested. Then waited two hours. Then four.

On the third test, the ice held.