Nitrous oxide, a.k.a. laughing gas, is an anesthetic chemical compound with medical uses in surgery and dentistry. It is used as a recreational drug and has been used as a Connection Supplement by Osho and American psychologist William James.
William James famously used nitrous oxide to trigger a mystical experience. His use of nitrous oxide convinced him that "our normal waking consciousness, rational consciousness as we call it, is but one special type of consciousness, whilst all about it, parted from it by the filmiest of screens, there lie potential forms of consciousness entirely different. We may go through life without suspecting their existence; but apply the requisite stimulus, and at a touch they are there in all their completeness, definite types of mentality which probably somewhere have their field of application and adaptation."
Since the preceding article was written, some observations on the effects of nitrous-oxide-gas-intoxication which I was prompted to make by reading the pamphlet called The Anaesthetic Revelation and the Gist of Philosophy, by Benjamin Paul Blood, Amsterdam, N. Y., 1874, have made me understand better than ever before both the strength and the weakness of Hegel's philosophy. I strongly urge others to repeat the experiment, which with pure gas is short and harmless enough. The effects will of course vary with the individual. Just as they vary in the same individual from time to time; but it is probable that in the former case, as in the latter, a generic resemblance will obtain. With me, as with every other person of whom I have heard, the keynote of the experience is the tremendously exciting sense of an intense metaphysical illumination. Truth lies open to the view in depth beneath depth of almost blinding evidence. The mind sees all the logical relations of being with an apparent subtlety and instantaneity to which its normal consciousness offers no parallel; only as sobriety returns, the feeling of insight fades, and one is left staring vacantly at a few disjointed words and phrases, as one stares at a cadaverous-looking snow-peak from which the sunset glow has just fled, or at the black cinder left by an extinguished brand. 
- Milne, H. (2015). Bhagwan: The God That Failed. Kindle Edition
- Huston, S. (2000). Cleansing the Doors of Perception. Boulder, CO: Sentient Publications.
- James, William. The Varieties of Religious Experience: A Study of Human Nature. New York: Penguin, 1982. https://amzn.to/2l4UyR7.
- James, William. The Varieties of Religious Experience: A Study of Human Nature. New York: Penguin, 1982.
- James, William. The Will to Believe and Other Essays in Popular Philosophy. Project Gutenberg, 2009. https://www.gutenberg.org/files/26659/26659-h/26659-h.htm.