In the past, some chemists believed that gold could be made from common materials. Some believed that since gold has a yellowish color, then yellow things, such as sulfur and even egg yolks could be changed into gold.
These scientists are called alchemists. When working on a recipe for gold some did not want to share their ideas, so they used mysterious looking diagrams that only they understood.
The alchemists who were more interested in scientific discoveries were more apt to share their ideas as well as any symbols they used in recording their procedures and results.