Ouroboros
For centuries, the ancient alchemists spoke in symbols and metaphors. Rather than communicate in concrete words, they preferred to use images or pictures, and singular words, names, titles, or phrases. The key idea was to keep it simple in order to boil it down to its essence.
The language they used was not necessarily just to serve the purpose of secrecy, though often that seemed to be the case, but rather it was in order to both not dilute the enormity or profundity of the ideas they were attempting to distill and communicate, as well what seems to aide in the simplicity and ease of preservation.
They used a whole slew of symbols to represent a myriad of concepts. But what alchemists were most known for is to reduce the seeming complexity of the world down to their simplest parts. In the mechanics of life or the meaning of it, they didn't see these as separate subjects; they didn't compartmentalize them or isolate so many self-considered academics do.
They were set on discovering the building blocks of not only life, but existence and the nature and meaning of it. In a time before the practices of modern scientific method, these philosophers were practical and thinking artists and artisans who sought to unite their unique and individual experiences of the world into a comprehendable unity of ideas. As they made discoveries, the alchemically minded would invent and identify images that most closely represented the ideas that they had discovered. It was this process whereby symbols became the way through which this dense and useful knowledge was once conveyed and taught.
One of the great symbols known and revered by the practitioners of alchemy is the ouroboros, or the snake eating his tail. Seen by most as a symbol of infinity, more specifically it is an embodied representation of the cycles of life, how the new emerges from the old, how the preparation leads to a fulfillment, how from a purpose emerges a plan, and perhaps how seasons repeat and lead one to another.
It also symbolized other things, most importantly the centrality of the idea of self sacrifice.