Halakhah sur Le Lévitique 20:27

That He prohibited us from doing the procedure of the yidaoni - and this too is one of the types of idolatry. And that is that one takes the bone of a bird, the name of which is yidoa, and places it in his mouth, burns incense, yells out and does [various] acts until he is visited by a state similar to a seizure and is overcome by a trance and speaks in clairvoyance. And they said (Sanhedrin 65b), "A yidaoni [is one who] places a bone of a bird, the name of which is yidoa, in his mouth, and [the bone] speaks on its own." And the prohibition about this comes with this language - "Do not turn to the ovot and to the yidaonim" (Leviticus 19:31). But do not think that this negative commandment is a general negative commandment. For He already separated it in the mention of the punishment and said, "or a yidaoni" (Leviticus 20:27). And he is punished for each one of them [with] stoning and excision, when volitional. And that is His, may He be exalted, saying, "A man or a woman who has an ov or a yidaoni [shall surely be put to death]." And the language of the [Sifra] (Sifra, Kedoshim, Chapter 10:1) is, "Since it says, 'A man or a woman,' we have heard the punishment. From where [do we know] the prohibition? [Hence] we learn to say, 'Do not turn to the ovot [and to the yidaonim].'"And for [violation of] this negative commandment inadvertently, one is liable for a fixed sin-offering. And the regulations of this commandment have already been explained in the seventh [chapter] of Sanhedrin. (See Parashat Kedoshim; Mishneh Torah, Foreign Worship and Customs of the Nations 6.)