I’ve had certain experiences where, when I’m in a state of ecstasy, I “see” something (but not “seeing” through the mode of medium understood as “my eyes”, but rather through another medium that exceeds human understanding). What is that “something” that I see?

I feel something like this:

I just feel like I keep "seeing" this disappearing piece to all of Reality. It's like a missing puzzle piece, and it completes the universe. I seem to not have this piece back when I was in "that world". It's just too "unreal" to believe back in "that world". A piece that's unable to be described back in "that world".

Then, when I leave that dimension and return here, I forget what I’ve seen.

The puzzle piece is missing again.

I’ve called this phenomenon “spiritual amnesia“, because it is a spell that’s cast on me that makes me repeatedly keep forgetting the revelations that I “see”.

What is it about the “ineffable”?

To me, the ineffable is an indication that there’s another world out there, a world that far transcends our normal earthly understanding. The existence of the ineffable, to me, is subjective proof of the existence of “other worlds” and “other realities”.

But, more miraculously, what does the perception of the “ineffable” mean for the nature of Self, existence, and world?

If our minds can perceive “ineffable worlds”, it throws into question the stability of our baseline way of looking at things. If we lack a sense for the mystical, how would we ever know we are missing it? How do we know of senses we do not have? Is that any indication for their non-existence?

Either way, the ability of the mind to perceive these “other worlds” seems to indicate that we live in a great imaginative-like multiverse, where we can travel psychically outside of space & time and into other dimensions. And our ignorance towards “other worlds” is merely a function of us coming from the perspective of any given world. In a certain sense then, we all have a window into the All.

What’s it like to get a temporary peak from another window?

Are those "somethings" aspects of a greater existence, distorted perhaps by the subject's perceptual filters? Are they first glimpses of a "larger earth"? To a frog with its simple eye, the world is a dim array of greys and blacks. Are we like frogs in our limited sensorium, apprehending just part of the universe we inhabit? Are we as a species now awakening to the reality of multidimensional worlds in which matter undergoes subtle reorganizations in some sort of hyperspace? Is visionary experience analogous to the first breathings of early amphibians? Are we ourselves coming ashore to a "larger earth"? 
~ Michael Murphy, The Future of the Body