Trepanning

Also known as trephining, this involves drilling a hole in the patient's head. It is believed this technique was used in prehistory to allow evil spirits a route out of the patient's head, to allow the patient to communicate with the spirit world, or to cure a headache! We know that some people survived these operations because there is evidence of healing in the skulls.

Modern evidence shows that repanning can lead to altered mental sensations, and some people have tried it for non-medical reasons. It's sometimes done by doctors when head injury has led to build-up of pressure within the skull.

The pineal eye is often considered in Eastern Religions to be the source of vision toward true enlightenment... sometimes the zealous attempt to "pry open" or "reveal" their pineal eye, otherwise known as the Third Eye, by way of trepanning, which is to expose the dura mater of the brain with a hole through the scalp and skull. Note, that besides the recent interest in this subject, it has been an observed practice for over 5000 years. Archeological records have recovered trepanned skulls from Peru, Libya, Melanesia, and India.

Trepanning is effective in expanding consciousness in that it allows more oxygen to the surface of the brain, but is very dangerous because bone splinters may damage brain tissue, not to mention the impurities in the air can damage neural tissue as well as enter the bloodstream.

Trepanning is not recommended.

...As for aforementioned eastern religion... there is recorded practice of Tibetans performing trepanations(trepanation being the singular verb in reference to a specific operation, whereas trepanning is the practice in general reference). T. Lobsang Rampa wrote about trepanation as spiritual initiation in his book, The Third Eye.