I'm not sure about a pharaoh's tomb, but there were rivers of mercury in the tomb of the first Emperor of China; also automatic crossbow traps I believe. It's the tomb with the Terracotta Army. Extremely fascinating.

1. futura-sciences.com - This Tomb is a Deadly Trap: Archaeologists Still Refuse to Open It

2. labrujulaverde.com - Rivers and seas made of mercury inside the tomb of China’s first emperor