Our ordinary minds are like a colloidal suspension of particles in constant Brownian motion - our consciousness zigs and zags under the bombardment of highly energetic thoughts and perceptions, scattered in a myriad of agitated fragments. The greater the “temperature” of the mind, the louder and more frenetic is the movement. The constant jostling of words, images, and sensations creates friction and heat, like a very active central processing unit in a computer.
What happens when we “chill out”? Lowering the temperature of the colloidal suspension causes the particles to lose kinetic energy and slow down. In the same way, steadfastly withdrawing the attention from the potpourri cascading into the mind through memory, sense organs, and thinking allows a “cooling” down towards less activity and greater calmness.
In physics, withdrawing heat from certain materials to reach very low temperatures, near absolute zero (approximately -273 °C or -460 °F), creates unusual quantum effects such as “superconductivity” (absence of resistance to the flow of electricity) and “superfluidity” (absence of viscosity, allowing liquids to flow against gravity).
Similarly, the practice of meditation permits engagement with the mind’s activities to decrease to near the “absolute zero” of total stillness and silence, clearing the usual perceptual and conceptual barriers that confine consciousness, which can then be experienced as limitless.
Dr. R. M. Bucke, a Canadian psychiatrist, described such an experience of “superconsciousness” in 1901:
“…there came upon me a sense of exultation, of immense joyousness accompanied or immediately followed by an intellectual illumination impossible to describe. Among other things, I did not merely come to believe, but I saw that the universe is not composed of dead matter, but is, on the contrary, a living Presence; I became conscious in myself of eternal life. It was not a conviction that I would have eternal life, but a consciousness that I possessed eternal life then; I saw that all men are immortal; that the cosmic order is such that without any peradventure all things work together for the good of each and all; that the foundation principle of the world, of all the worlds, is what we call love, and that the happiness of each and all is in the long run absolutely certain. The vision lasted a few seconds and was gone; but the memory of it and the sense of the reality of what it taught has [sic] remained during the quarter of a century which has since elapsed. I knew that what the vision showed was true.” 
Others have used different words to describe what is inexpressible but what we all know intimately: the fullness of simple being and awareness, containing all and embracing all, without the habitual fetters of self-limiting concepts and frameworks. This is indeed the starting point, the beginning of any scale, the original placeholder, the naught or cipher that makes all subsequent numeration possible.
 William James, The Varieties of Religious Experience: A Study in Human Nature, p. 399; New York: Longmans, Green, 1911