Staring at a stone (self-hypnosis) or meditation, etc., do not produce florid psychotic symptoms. Here is an example of the kind of episode I am referring to as recorded in Times and Seasons.
--- we partook together of the emblems of the body and blood of our Lord Jesus Christ … and the Holy Ghost was poured out upon us in a miraculous manner many of our members prophesied, whilst others had the heavens opened to their view, and were so overcome that we had to lay them on beds, or other convenient places: among the rest was brother Newel Knight, who had to be placed on a bed, being unable to help himself. ... He saw the heaven opened, and beheld the Lord Jesus Christ seated at the right hand of the Majesty on high ... When bodily strength was restored to these brethren, they shouted `Hosannas to God and the Lamb,' and rehearsed the glorious things which they had seen and felt, whilst they were yet in the spirit. (Times and Seasons, Vol.4, No.2, p.22-p.23)
Note that this episode started with a taking of the sacrament (wine at that time). Note that Bro. Newell "had to be placed in bed, being unable to help himself".
Note that one of the recognized symptoms of intoxication by certain entheogins is "prophetic utterances". (See the graphic on the "Heaven" thread.)
The account above says that they rehearsed things which they had "seen and felt". Bro. Newell saw exactly what the magician Joseph Smith had suggested that he would see. (Richard Bushman has characterized Joseph Smith as a "magician" - his words not mine.)
Datura poisoning is not a passive "lay back and enjoy" experience such as has been reported for DMT. It is characterized by by increased heart rate, sweating, agitation, dizziness, etc. It is something that is really "felt" physically.
There are several recorded occasions where Joseph Smith told his followers, "now we are going to see visions", pretty much the same way in which a Shaman tells those in his charge what to expect on their vision quest.
When one looks at the evidence with some understanding of the use of enthoegens in 19th Century America, things become pretty clear.
As for recorded use of these substances by European Americans, you have a good point. I do know of some evidence that this was the case, but the question certainly deserves more attention.