octavo

noun

1. A sheet of paper 7 to 10 inches (= 17.78 to 25.4 cm) high and 4.5 to 6 inches (= 11.43 to 15.24 cm) wide, the size varying with the large original sheet used to create it. It is made by folding the original sheet three times to produce eight leaves.
2. A book of octavo pages.

   “He was also much of a politician; too much, perhaps, for his station. There fell lately into my hands, in London, a collection he had made of all the principal pamphlets, relating to public affairs, from 1641 to 1717; many of the volumes are wanting as appears by the numbering, but there still remain eight volumes in folio, and twenty-four in quarto and in octavo.”