From the Biblia Pauperum. Block Book. 15th Century.details

In the later Block-books, engraved sentences and even half-pages of explanation are seen. The dislike of wood engravers to cut letters is the same now as it was four centuries and a-half ago, the mechanical nature of such work being distasteful to any one with artistic feeling. The idea, therefore, or using a second time sentences, already engraved and printed, simply by cutting them away from the old block, was very natural and would easily lead to the attempt to utilise the letters separately. Thus we float along the stream of gradual development, until we reach ovable types, properly termed Typography. This was never an invention pure and simple which suddenly enlightened the mind of Gutenberg (as stated by Van der Linde, and echoed by Theo. De Vinne), but an end successfully accomplished, after numerous efforts and gradual advances.*

[footnote: * The reader who has any real interest in the “firstlings” of the Printing-press should carefully examine the glass cases in the Grenville Library at the British Museum, where specimens of Block Printing, from the earliest to the latest, are displayed in chronological order.] (p. 9)