| Return to Julius Caesar, Act 1, Scene 2, line 246 |
I believe that the kind of cap Shakespeare had in mind was the knitted woollen flat cap, such as the one at the left.
In 1571, when Shakespeare was 6 years old, a law was passed in England which mandated that everyone above 6 years of age wear a woolen cap on Sundays and holidays. The law—intended to boost the English wool trade—really only applied to the lower classes, as the higher classes already had the lawful right to wear higher hats, such as the leather and silk model seen below:
As for the Romans of the time of the historical Julius Caesar, there were very few headwear requirements. Soldiers wore helmets into battle, and priests had special togas which included a head flap which could be used when a ceremony required the head to be covered, but as a general rule, Romans went bare-headed.