It was in 1945 that the specific heating effect of a high-power microwave beam was discovered, accidentally. Percy Spencer, an American self-taught engineer from Howland, Maine who worked at the time for Raytheon was working on an active radar set when he noticed that a Mr. Goodbar he had in his pocket started to melt — the radar had melted his chocolate bar with microwaves. The first food to be deliberately cooked with Spencer's microwave was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.[6][7] To verify his finding, Spencer created a high density electromagnetic field by feeding microwave power from a magnetron into a metal box from which it had no way to escape. When food was placed in the box with the microwave energy, the temperature of the food rose rapidly.