Offerings of jade celts and figures seem to be commonplace and were likely concentrated in burials (though this cannot be confirmed because there are no human remains still present). Artifacts, such as jade earspools, beads, pendants, spangles, plaques, and other jewelry, were found in plenty at burial sites; however it is difficult to tell if they were worn or placed in the grave as burial goods. Structure A-2 (Mound A) is an earthen platform thought to be a burial site (a "funerary chamber"). Inside the platform, researchers discovered badly preserved bones covered in a red pigment, cinnabar, a substance used in similar Mesoamerican cultures to denote status. Also found were jade artifacts, figurines and masks, as well as polished obsidian mirrors. Mirrors are also suspected to be a mark of rank among the Olmec, as stelae and other monuments display leaders and priests wearing them on their chest and on their foreheads. "Throughout the layer [uncovered by Stirling in 1942] were copious unrestorable traces of organic material. The red cinnabar lay in a fashion which gave the impression that it had been inside of wrapped bundles. Probably the bodies had been thus wrapped before interment." Rust (2008) discovered "urn burials" in Complex E (residential area) where fragments of bone and teeth were buried in clay pots. "The fill immediately around this large urn was clean, yellow sand, and the urn was covered with an inverted fine-paste orange bowl with flaring walls; the bowl's interior was painted red and incised with the double-line-break pattern on the inside rim." "For decades, certain scholars have used shamanism as an explanatory paradigm for considering the monuments of La Venta... one of the most important ceremonial-civic centers of the Middle Formative era. Most of what is known about Olmec religion is speculative, but certain patterns do emerge at La Venta that are certainly symbolic and might have ritual meaning. For example, the crossed bands symbol, an X in a rectangular box, is often repeated in stone at La Venta, other Olmec sites, and continued to have significance to the cultures inspired by the Olmec. It often appears in conjunction with the maize deity and so might have connection with subsistence. The artifacts discovered at La Venta have been crucial to starting to understand Olmec religion and ideology.