What were the first methods of placer mining used?

Placer mining (pronounced plasser, BTW) is mining for gold that is free of the rock. This is usually in the form of gold dust and fine nuggets. The simplest means, and the first used, was panning for gold in the rivers. You can also used a sluice box, where sand is shoveled into a trough with water running through it. Running water carries away lighter materials, and leaves the heavy gold in grooves on the bottom of the sluicebox.