The name 'Easter Island' was given by the island's first recorded European visitor, the Dutch explorer Jacob Roggeveen, who encountered it on Easter Sunday April 5th in 1722, while searching for 'Davis Land'. Roggeveen named it 'Paasch-Eyland' (18th-century Dutch for Easter Island). The island's official Spanish name, 'Isla de Pascua', also means 'Easter Island'. Oral tradition has it that the island was first named 'Te pito o te kainga a Hau Maka', meaning 'The little piece of land of Hau Maka'. Another name, 'Mata ki te rangi', which means "Eyes looking to the sky". The large stone statues, or moai, for which Easter Island is famous, were carved in the period 1100–1680 AD. A total of 887 monolithic stone statues have been inventoried on the island and in museum collections. Although often identified as 'Easter Island heads', the statues have torsos, most of them ending at the top of the thighs. A small number are complete figures that kneel on bent knees with their hands over their stomachs. Some upright moai have become buried up to their necks by shifting soils. Almost all moai were carved from compressed, easily worked solidified volcanic ash or tuff, found at a single site on the side of the extinct volcano. Only a quarter of the statues were installed. Nearly half remained in the quarry, and the rest sat elsewhere, presumably on their way to intended locations. The largest moai raised on a platform is known as 'Paro'. It weighs 90 tons and is over 32 feet high. Several other statues of similar weight were transported to the north and south coasts. Petroglyphs are pictures carved into rock, and Easter Island has one of the richest collections in all Polynesia. Around 1,000 sites with more than 4,000 petroglyphs are catalogued. Designs and images were carved out of rock for a variety of reasons: to create totems, to mark territory, or to memorialize a person or event. There are distinct variations around the island in the frequency of themes among petroglyphs, with a concentration of Birdmen at Orongo. Other subjects include sea turtles, Vulvas and Makemake, the chief god of the Tangata manu or Birdman cult.