mushrooms. The drug is more stable in dried than fresh mushrooms; dried mushrooms retain their potency for months or even years, while mushrooms stored fresh for four weeks contain only traces of the original psilocybin. The psilocybin contents of dried herbarium specimens of Psilocybe semilanceata in one study were shown to decrease with the increasing age of the sample: collections dated 11, 33, or 118 years old contained 0.84%, 0.67%, and 0.014% (all dry weight), respectively. Mature mycelia contain some psilocybin, while young mycelia (recently germinated from spores) lack appreciable amounts. Many species of mushrooms containing psilocybin also contain lesser amounts of the analog compounds baeocystin and norbaeocystin, chemicals thought to be biogenic precursors. Although most species of psilocybin-containing mushrooms bruise blue when handled or damaged due to the oxidization of phenolic compounds, this reaction is not a definitive method of identification or determining a mushroom's potency. History Early There is evidence to suggest that psychoactive mushrooms have been used by humans in religious ceremonies for thousands of years. 6,000-year-old pictographs discovered near the Spanish town of Villar del Humo illustrate several mushrooms that have been tentatively identified as Psilocybe hispanica, a hallucinogenic species native to the area. Archaeological artifacts from Mexico, as well as the so-called Mayan "mushroom stones" of Guatemala have also been interpreted by some scholars as evidence for ritual and ceremonial usage of psychoactive mushrooms in the Mayan and Aztec cultures of Mesoamerica. In Nahuatl, the language of the Aztecs, the mushrooms were called teonanácatl, or "God's flesh". Following the arrival of Spanish explorers to the New World in the sixteenth century, chroniclers reported the use of mushrooms by the natives for ceremonial and religious purposes. According to the Dominican friar Diego Durán in The History of the Indies of New Spain (published c. 1581), mushrooms were eaten in festivities conducted on the occasion of the accession to the throne of Aztec emperor Moctezuma II in 1502. The Franciscan friar Bernardino de Sahagún wrote of witnessing mushroom usage in his Florentine Codex (published 1545–1590), and described how some merchants would celebrate upon returning from a successful business trip by consuming mushrooms to evoke revelatory visions. After the defeat of the Aztecs, the Spanish forbade traditional religious practices and rituals that they considered "pagan idolatry", including ceremonial mushroom use. For the next four centuries, the Indians of Mesoamerica hid their use of entheogens from the Spanish authorities.