In 1997, Mark Lehner and stonemason Roger Hopkins conducted a three-week pyramid-building experiment for a NOVA television episode. They built a pyramid 6 metres (20 ft) high by 9 metres (30 ft) wide, consisting of a total of 162 cubic metres (5,700 cu ft), or about 405 tons. It was made out of 186 stones weighing an average of 2.2 tons each.