Friendly fish.

From a 14th-century illuminated manuscript of Jacob van Maerlant's Der naturen bloeme (The flower of Nature). More here: https://publicdomainreview.org/collection/jacob-van-maerlant-der-naturen-bloeme #fridayfish

Der Naturen Bloeme: The Flower of Nature (ca. 1350)

Early Dutch illuminated manuscript containing imaginative images of both real and fantastic creatures.

The Public Domain Review