““Underlying all this activity—in the customhouses, on the wharves, in every place of business—were numbers. Merchants measured out their wares and negotiated prices; customs officers calculated taxes to be levied on imports; scribes and stewards prepared ships’ manifests, recording the values in long columns using Roman numerals. They would have put their writing implements to one side and used either their fingers or a physical abacus to perform the additions, then picked up pen and parchment once again to enter the subtotals from each page on a final page at the end. With no record of the computation itself, if anyone questioned the answer, the entire process would have to be repeated.””
