>"Trying to sit still for 30 min without any stimulation at all (no talking, watching, reading) sounds like torture to me"

I've done more than that. Summer time I often swim in open water up to 2 hour at once as one of the ways to stay fit. Obviously it becomes routine and not very entertaining. So I usually doing some high level software design work in my mind at this point, exploring some concepts, thinking business ideas etc. etc. So my body does monotonous work of not very high intensity and my brain is busy with everything else. Not board at all.

I once spent 1.5 hour standing in a church listening to a priest for more than an hour (funeral). Same thing I mentally solved the problem why some piece of my code did not work.

Without this ability I would go nuts. My brain always has to be busy with something. It is like a drug for me.

Try ultra running for at least 10 hours. You run out of things to think about, plus you are so tired that you cannot concentrate for long on the same subject.

After some struggle you will enter into a weird state that I think should be similar to what they achieve through meditation.