An abacus is an ancient tool used for counting ... although the oldest counting boards have been found in fourth century BCE Rome. Many cultures used abaci or something similar (such as the Inca quipu ...

The abacus is believed to be the first version ... We take running water for granted today, but ancient Rome first devised this ingenious idea. Using gravity, the Romans created arched structures ...

And so did the ancient Romans. Their counting devices ... and from contemporary devices found in Greece, the standard Roman abacus used glass, ivory, or bronze counters placed on a board marked ...