48mo

The generally used descriptions of size, from folio down to 48mo. signify no accurate measurement whatever, the same book being described by different catalogues as 12mo. 8vo, crown 8vo. &c., according to fancy; while the same cataloguer who describes a volume as octavo to-day, is very likely to call it a duodecimo to-morrow.

A Book for All Readers An Aid to the Collection, Use, and Preservation of Books and the Formation of Public and Private Libraries Ainsworth Rand Spofford