MLA

Chaucer, Geoffrey, -1400. A treatise on the astrolabe. Box. [ca. 1450]. https://collections.library.yale.edu/catalog/16371205.

APA, 6th edition

Chaucer, Geoffrey, -1400. (["Box"])([ca. 1450])[A treatise on the astrolabe]. https://collections.library.yale.edu/catalog/16371205.