The oracle itself is not a myth but I think the prophecies and how they prophecy in that place is the myth. In those days, people seek the oracle for answers and they thought the answers are channeled through young girls who are possessed by gods but instead are high in drugs.
I see what you mean but this site clearly indicates the use of some form of gas. Do you think the people who visited were unaware of this? I just read this article which suggests that nobody involved really planned it this way. It's a mystery I would love to solve!
I had to write a paper about the Oracle of Delphi. It was a long time ago, and I've forgotten most of the details. It has been suggested that the Pythoness was positioned over a fissure in the earth which vented some sort of intoxicating gas.
I've heard about the "Delphic Oracle" - and presume it's the same one that RLynn write about. She figues in both the book "I, Claudius" by Robert Graves and in the TV series based on the book. The Emperor Claudius wrotes a "warts and all" history of his family after the Oracle told him that it would survive for over a 1000 years before being discovered to reveal the truth.
I actually saw the ruins of the temple of Apollo when I visited Delphi in '95. The guide pointed to the part where the oracle sat. I think it is still debated as to whether she became intoxicated by fumes from a fissure in a rock and fell into a trance.
However it is not necessary; people always work themselves into trances when they think a god is upon them. Modern day witches do it when they "draw down the moon." And Voodoo priestesess do it when a god is "riding them."