Mesoamerican cosmologies and iconography. World trees embodied the four cardinal directions, which represented also the fourfold nature of a central world tree, a symbolic axis mundi connecting the planes of the Underworld and the sky with that of the terrestrial world. Depictions of world trees, both in their directional and central aspects, are found in the art and mythological traditions of cultures such as the Maya, Aztec, Izapan, Mixtec, Olmec, and others, dating to at least the Mid/Late Formative periods of Mesoamerican chronology. The tomb for the Ancient Maya king, K'inich Janab' Pakal I of Palenque who became King at only 12 years old has Tree of Life Inscriptions within the walls of his burial place, showing just how important it was to the Maya people. Among the Maya, the central world tree was conceived as or represented by a ceiba tree, and is known variously as a wacah chan or yax imix che, depending on the Mayan language. The trunk of the tree could also be represented by an upright caiman, whose skin evokes the tree's spiny trunk. Directional world trees are also associated with the four Yearbearers in Mesoamerican calendars, and the directional colors and deities. Mesoamerican codices which have this association outlined include the Dresden, Borgia and Fejérváry-Mayer codices. It is supposed that Mesoamerican sites and ceremonial centers frequently had actual trees planted at each of the four cardinal directions, representing the quadripartite concept. World trees are frequently depicted with birds in their branches, and their roots extending into earth or water (sometimes atop a "water-monster," symbolic of the underworld). The central world tree has also been interpreted as a representation of the band of the Milky Way. North America In a myth passed down among the Iroquois, The World on the Turtle's Back, explains the origin of the land in which a tree of life is described. According to the myth, it is found in the heavens, where the first humans lived, until a pregnant woman fell and landed in an endless sea. Saved by a giant turtle from drowning, she formed the world on its back by planting bark taken from the tree. The tree of life motif is present in the traditional Ojibway cosmology and traditions. It is sometimes described as Grandmother Cedar, or Nookomis Giizhig in Anishinaabemowin. In the book Black Elk Speaks, Black Elk, an Oglala Lakota (Sioux) wičháša wakȟáŋ (medicine man