Now, the תשורת שי that I mentioned above already prohibits the practice of divining the future by means of a table of letters- even if children are involved. Certainly, that posek was aware that prophecy is found amongst children- and yet he forbade the practice anyway. Why? I suppose it's because of the methodology.Indeed, having seen videos of Jewish facilitated communication, it is indeed like an Ouija board, with the facilitator grabbing the autistic's hand and making it point to various letters on a page, often with the autistic person closing his/her eyes and looking the other way. In both cases, the scientific explanation of the phenomenon is the ideomotor effect.
I don't know that pointing to a halachic condemnation of the practice, and trying to argue against the practice in this way, will succeed. Indeed, it sets the stage for counter-argument based on Rabbi X or Rabbi Y approving it. (For example, HaRav Hagaon Rav Nosson M. Wachtfogel, zt"l "approved" it. Of course, these folk only consider him HaRav HaGaon Rav because he supports a belief they want to believe; his haskama explains that he didn't read the darn book but he trusts the person who said it was good stuff -- just as Rav Chaim Kanievsky trusted others about Elior Chen's innocence and so signed onto a letter of support. And, of course, he he stresses one should not use it to practical end, but should rather follow rabbis, who are the leaders of klal Yisrael. The foolish people then take this as support for autistics as neviim that one should follow in practical matters, instead of following their rabbis.)
Maybe more on this later. For now, here is a rough translation of the teshuva. There were a few places I could not make sense of the words. Comments welcome in this, and other, regards.
The teshuva in question, from Rabbi Shlomo Yehuda Tabak (d. 5668), follows. It regards the use of an Ouija board, and a planchette - a small three-legged 'table' positioned over the board, to point to the letters. See the image to the right so that you understand what the teshuva is describing.
"129: Question: A Jewish man came from Eretz Yisrael and fashioned for himself a small table upon three legs, and under the table is a tray or page upon which are written all the letters of the aleph-beis on one side, and upon the second side are the secular letters. And five children stand around him and rest their hands upon him. And Jews and gentiles go to him to ask of him the future, whether in matters of shidduchim or travels, and upon many similar matters. And he asks the question and the table lifts one of its legs and displays the letters to combine to arrive at the answer. And he works great wonders with the questioners, which are concealed from the eyes of the intellect. And I heard that he first goes to the mikveh and says a certain chapter of Tehillim, and that he says that this is a chochmah (a craft / science) and there is no magic or incantations involved. And that he learned this craft from a great Torah scholar and God-fearing individual, and that also, there, in Eretz Yisrael, great and holy tzadikim make use of this. And it appears that [Iyov 15:15] הֵן בִּקְדֹשָׁו לֹא יַאֲמִין, "Behold, He [Hashem] putteth no trust in His holy ones [these tzadikim]" since regardless, it is forbidden to ask [in this manner] because of [Devarim 18:13] תָּמִים תִּהְיֶה עִם ה אֱלֹקֶיךָ, "Thou shalt be whole-hearted with the LORD thy God", as is stated in [Shulchan Aruch] Yoreh Deah at the beginning of siman 179.
However, there is to say that a single witness is believed in matters of prohibition [eid echad neeman be'issurin] to everyone, when the prohibition is not established [lo itchazik issura], and he is not invalidated because he causes others to stumble in the prohibition of תָּמִים תִּהְיֶה, for this is not as stringent as one who performs acts of divination, and as is stated in Terumat Hadeshen in pesakim uchtavim [rulings and writings] siman 96. And further, people do not generally understand this to be prohibited, whereas divination everyone knows that it is prohibited.
However, this is difficult to believe, for I think that this is in the realm of kosem kesamim [engaging in divination], for there are many different sorts of divination For the Rambam writes about it in one way, and the Semag [Sefer Mitzvot Gedolot] in another way, and Rabbeinu Yerucham wrote that they make points [?] in writing or in sand, and similar matters to this. And the intent is to say that that which is not [?] of the natural order and intellect is divination. Thus, these questioners [to the man with the Ouija board] are adding upon תָּמִים תִּהְיֶה, the prohibition of 'put not a stumbling block before the blind' [causing someone else to sin] for divination is punished with lashes if they ask from a Jew.
And further, regarding how five children stand around him and rest their hands upon him, and that he also says beforehand some chapter of Tehillim, it seems that he is performing some act utilizing demons and is afraid lest they harm him, and as is states in Bet Yosef and Rama in Yoreh Deah siman 179, that most who engage [with them] do not go away from them in peace [unharmed]. And it is made clear in Bet Yosef, and in Shulchan Aruch, and in the Shach there, seif katan 120, that if he performs some act, it is prohibited. And in the language of Rabbeinu Yerucham, brought down in Bet Yosef, which is that if he takes something and using it performs some act, this is called an act of divination."