I was one of those kids who were taught that meditation and yoga cleared one's mind for demonic influence. Also, those really cool "magic eye" images (famous books were made about them in the 90s), where you have to kind of cross your eyes to see it? Yup, that was teaching you to use your demonic "third eye" that Eastern religions talked about.
If you were worshipping a God that wasn't "The God" (New Testament version of the Biblical God), then what you were worshipping was Satan. Even atheists "worship" Satan since all of their actions are not in service of God. If you're doing a practice that came from another religion (in this case, according to them, yoga), you're also worshipping Satan, even if you think you're doing it for the glory of God! (For instance practicing yoga to help with the upkeep of God's temple, which is your body). I was taught that every single action we do is either for the glory of God, or not. It's really quite funny because all of our holiday traditions are pretty much taken from other religions, but they just kinda don't teach about that.
My guess is you don't live in a super Bible-belt type area, because none of these teachings were uncommon among classmates/friends' experiences. (I live in the U.S. South in a very Christian area). The constant stress of wondering if your actions are truly in service of God was so fucking intense, I don't miss it. And I didn't even come from one of the super fundie families.
If you want to learn to do it on command get a Magic Eye book to practice. Most libraries have them.
Buy one of the Magic Eye books from amazon and practice letting your eyes relax, almost letting your eyes gaze into the distance. The images will seem blurry and then pop out at you.
https://www.amazon.com/Magic-Eye-New-Looking-World/dp/0836270061
*magic eye, but here is an amazon link for reference: https://www.amazon.com/Magic-Eye-New-Looking-World/dp/0836270061
It even says so on the back of the book: https://www.amazon.de/Magic-Eye-New-Looking-World/dp/0836270061
Found one of these on Amazon just to let my kids try. 📦 Amazon📦
You should check out this book called magic eye
https://www.amazon.com/Magic-Eye-New-Looking-World/dp/0836270061
I don't really recall, but I ended up buying this book. Also got the second edition.