bishop's length

Century Dictionary and Cyclopedia

1. n. In painting, canvas measuring 58 inches by 94. The half-bishop measures 45 inches by 56.

Wiktionary

1. n. An old portrait size, measuring 58 by 94 inches.

GNU Webster's 1913

1. A canvas for a portrait measuring 58 by 94 inches. The half bishop measures 45 by 56.