Arnaud Delormes scientific studies about meditation are helpful, but also Sadhgurus reports about self-experienced mental states

The Reality of Meditative States ~ Arnaud Delorme: Sadhguru’s Enlightenment – In His Own Words Not everything we experience can be measured. And we don t believe in scientists who only believe in things that can be measured. They often are not self-experienced. We doubt about scientists who only believe in things they can measure. …