Early representations tended to show them dressed in vaguely classical garb. He holds a staff in one hand and in the other a book and a sprig of mistletoe. A bag or scrip hangs from his belt. The main sources we have on what Druids did are the teachings and writings of Roman historians, such data as archeological remains can provide, and mythological literature recorded by monks in the eighth through twelfth century. Also, analogies can be drawn between the Celts and such Indo-European cultures that existed around the same time and had the same level of cultural achievement, such as the Hindu people.
Archaeology is an excellent resource for the study of celtic history.
There are also the remains of celtic fortresses, habitations, temples, jewelry and tools. These facts about Celtic social life are an important element for understanding Druidism, because it is necessary to understand the whole culture in which Druidism was situated. Posidonius was trying to fit the Druids into his own Stoic philosphy. There is also an attempt to cast the old Celts in the role of the innocent and wise noble savage, uncorrupted by civilisation and close to nature, as in the case of the writer Tacitus. Nevertheless they were often impressed by the Druids' grasp of mathematical and astronomical skill.