In the 1970's some scientists from major US universities convinced Indian gurus to travel to their labs where they got tested using EEG machines. The results of the experiments showed that, while people are alert and under normal conditions, the EEG machines recorded beta brainwaves. However, then they started meditating they got into alpha, theta and delta brainwaves. Many more measurements were made to match brainwaves with emotional states. If you look at the work by Anna Wise, in one of her books she describes how to meditate to create certain brainwaves. She has been using an EEG-besed device called Mind Mirror to collect her results.
If you have some spare US$2000 or so, you can buy a small EEG machine and measure your own brainwaves. The interpretation of the results is not as simple as personal development gurus make it. You also need to add costs of consumables, like electrodes, adhesive paste, etc. Go to
http://www.transparentcorp.com/ and you can find one of these machines.
