The Oracle of Dephi was huffing

Seems that the gases being emitted from the earth that gave her visions was ethylene.

Ethylene inhalation is a serious contender for explaining the trance and behavior of the Pythia," said Diane Harris-Cline, a classics professor at The George Washington University in Washington, D.C.

"Combined with social expectations, a woman in a confined space could be induced to spout off oracles," she said.

According to traditional explanations, the Pythia derived her prophecies in a small, enclosed chamber in the basement of the temple. De Boer said that if the Pythia went to the chamber once a month, as tradition says, she could have been exposed to concentrations of the narcotic gas that were strong enough to induce a trance-like state.