What interests me in mysticism (especially the via negativa of Middle-Ages theologians, which echoes much Eastern philosophy) is not supranaturalism.
Rather its pointing to an internal limit of language and conceptualisation, hence reason.
It is not to be thought of as an external border, on the far side of which would lie or stand "something" unattainable through language. Language potentially encompasses everything, what is and what is not, as it creates its own realm of fiction -- indeed making any naming or description of what would lie beyond language a self-delusion, practically undistinguishable from fiction.
The internal limit I refer to is the following: as I name things, my grasp on them is limited to the things as named, iow to signifiers; actually, only my naming makes them "things" separate from other "things" in my imaginary "reality". To allude to a well-known buddhic example, there remains an essential, yet strictly ineffable, difference between the actual rose before me and my description of "it", however precise. What before me remains indifferent to the word "rose" as to the depiction and measurements of colour, size, form, smell, touch, and is not separable from what I call the stem, the plant, the ground, the air or the sun, this I cannot really name nor describe. Even if I call it being, à la Heidegger, I have just made up another concept which is not "it" either. What is not enlightened by the light of the logos-ratio I simply cannot tell but I know it ek-sists, "outside language" as it were and yet within every "thing" named through language. Or, more exactly, I know that whatever I know is not all that is, and actually is not at all. There is an unsuperable separation (the Lacanian "symbolic cut" if you will) between what I name "a rose" and
a rose (which I can only refer to by naming and erasing).
"Mysticism" to me is nothing but a pause, or silence, on the edge of language. Not stepping out of language ("I" cannot) but feeling the inner limit of language from within language. This sometimes results in a different way of speaking -- perhaps an even more indirect, metaphorical one. Strangely enough, you might "see" the rose better through poetry than through botanics -- even though the latter can prove quite helpful too.