Cite

[Frederic discovering the skeleton near the altar] [art original].

MLA

[Frederic Discovering the Skeleton near the Altar] [Art Original]. 0AD. https://collections.library.yale.edu/catalog/16704400.

APA, 6th edition

[Frederic discovering the skeleton near the altar] [art original]. (0 C.E.). [Illustrations, Watercolors British 19th century]. https://collections.library.yale.edu/catalog/16704400.