Interpreted through a lens where the "above" corresponds to the mental, ideal, immaterial, the rational and the irrational, what can be very loosely referred to as "the psyche;" and the "below" corresponds to the physical world, governed by the laws of nature; this maxim can be understood to mean, "as exists in the psyche, so in the physical world; as exists in the physical world, so in the psyche."
Our psychological state influences our course of action in the physical world, and the response we get from the physical world in turn influences our psychological state in a mutually reciprocal relationship. What is more significant than just one or the other is the relationship between the psychological and the physical; how thoughts can precede actions, and how actions can cause reactions within the psyche (this is how I understand what Daniel M. Ingram refers to as "Cause and Effect" in his text, "Mastering the Core Teachings of the Buddha" [0]).
Reality exists between these two poles, in that we interpolate between the discrete, moment-to-moment perceptual data we receive from the five sensory organs, as well as the intellectual, intuitive, & psychological data we receive from the sixth "sense door" of mind, in order to construct a continuous view of the world. Thus, I would hazard to claim, if we wish to alter (at least our subjective, or "microcosmic" lens on) our reality, we have the option of either perturbing our psychological state (the way of the Jungian analyst, the mystic, the Yogi, the devotee, and so on), or our physical state (by altering our mundane life circumstance, diet, lifestyle, and so on).
I view psychedelics as instrumental in probing the boundary between these two poles of this mutually reciprocal relationship between mind and body, being chemical (physical) agents that induce immediately apparent effects within the psyche; they allow one to explore the ways in which perception and our internal, psychological reactions to that perceptual data are related. Psychedelics are a unique tool that allow one to alter (however crudely, imprecisely, and quantifiable only in the loosest of senses) their psychological parameters in such a way that allows for, at the very least, the base realization that:
there is more than one way to think about and perceive the world.
To the extent that our thoughts and perceptions about the world influence our actions within it, and the feedback we receive from it, it is at least interesting to temporarily inhabit different ways of apprehending it, to come to a more diverse view of reality that has appreciated it, if only briefly, from multiple different angles. The insights we may or may not arrive at, having contemplated our view of reality from a different vantage point, may reconfigure our internal psychological state in a way that influences future action.
The alchemical goal of the transmutation of base metal into gold was more than a physical pursuit; it was a spiritual one, whose object was the reconfiguration of the base psyche, victim to the whims and vicissitudes of the urges and desires of the animal self, into "enlightened" consciousness, continuously aware, present, and able to choose on a moment-to-moment basis the next course of action, however subtle. Through the reconfiguration of one's psyche in a permanent and lasting manner (the "magnum opus"), by the Hermetic axiom aforementioned, one is able to forever reconfigure their relationship to the physical world and (purportedly) act within it in a manner that more closely coheres with one's personal view of "what is right."
[0] https://www.mctb.org/mctb2/table-of-contents/part-iv-insight...