30:1 · The circle divided by a horizontal line is a structure often found on rock carvings. In early Chinese calligraphy it represented the sun(the earliest sun sign was , though). In the Greek alphabet the structure is used to signify the letter theta. The sign is used in at least ten different ideographic systems of natural science, and in the new religion conceived by the late science fiction writer and philosopher L. Ron Hubbard half a century ago, Scientology, it is a symbol for the individual human spirit.
The alchemists used to denote salt (more usually drawn or ).
In a system of the four elements that is Spanish in origin, we find meaning water (the others are for earth, for fire, and forair).
This sign is generally associated with the idea of something absolute, e.g. absolute time, absolute temperature, absolute center etc. With regard to this, can be said to be synonymous with .
In other modern systems is used to mean stop or end.