 In Gauss's conception, this was drawn in its modern form, it is 

After the discovery of Vesta, no further objects were discovered for 38 years, and the Solar System was thought to have eleven planets.However, in 1845, new asteroids started being discovered at a rapid pace, and by 1851 there were fifteen, each with its own symbol, in addition to the eight major planets (Neptune had been discovered in 1846).It soon became clear that it would be impractical to continue inventing new planetary symbols indefinitely, and some of the existing ones proved difficult to draw quickly.