I first learned about what I personally call the “Second Layer” from someone who had a rather personal experience with psychedelics, and a claim that many had seen a world which was so bizarrely different from ours. A world in which we are both everything and nothing. A continuous stream of compound existence which our minds ordinarily keep us from accessing by proxy of possessing a sense of individuality. Through meditation, it is possible to create a state in which you can incite an “Ego Death”, in which you temporarily reject this individuality and merge your existence and spirit into the stream.
While within the stream, you will ordinarily be greeted by an environment that's, to put it simply, psychedelic in nature. The environment and colors around you are always warping, twisting, and contorting, flowing like water, yet you can still barely make out individual figures amongst the streams. The place which most tend to end up, and where I also did, was a “Waiting Room”, in which a hawk-like humanoid stopped me, telling me that I should never had gotten that far. He was a Guardian, his mission being to keep those who weren't supposed to access the stream from doing so. As you must incite a spiritual Ego Death in order to get that far, your sense of self-preservation will no longer be maintained by your brain, and you'll typically stop breathing involuntarily within a few minutes. Despite this risk, and with my time limit in mind, I asked if he would be my Guide, to which he agreed. As we exited the Waiting Room, I saw a rather vast landscape of colors, with beings of various shapes and sizes roaming about without much of a care or paying me any heed. We were all part of the same stream of energy, so why should they care?
He informed me of the nature of that place, and that the human mind was typically kept from accessing the stream for the reasons I demoted above. A confirmation of what I had heard from the other visitors, and that I would die within 20 years of something that I could prevent. What that was, he didn't get to tell me. My time ran out and the body started to choke, during which I bid my farewell and retreated back into the First Layer. Paralysis came first, though Ayumu was a dear and helped reacquaint my spirit to the First Layer. It was then I heard the voice of the Guardian, with him telling me that I was always welcome to return to the Second Layer should I wish to.
How could I not? My fascination with that world piqued after seeing it for myself, and I believe there's much more to discover in the world beyond our own.
What's even more bizarre is that being under the influence wasn't necessary for me to get there. Whether or not it mattered or affected the duration of a visit, I don't know, but my personal code keeps me from finding out whether that's the case or not. A few minutes is more than enough.