John Trapp on Job 41:24

Verſe 24. His heart is as firm as a ſtone] He is corpore & corde validiſſimus. Of the ſword-fiſh, Plutarch ſaith, that he hath a ſword, but not an heart to uſe it. But the Whale hath courage to his bulk; his heart is as firm as a ſtone, [non-Latin text not transcribed]. as his head (ſaith Scaliger) is as hard as a flint. In the hearts of ſome creatures, ſaith Ariſtotle, is found a bony, or griſly hardneſs; but the Whales heart is all as it were a bone; and this bone as a ſtone.

As a pair of the neather milſtone] Metae, upon which the whole weight lyeth: the Greek call it [non-Latin text not transcribed], Mat. 18.6. the Mill-Aſs; becauſe it is the bigger and harder of the two. The vulgar here for the neather Mill-ſtone, hath the ſmiths-Anvil, which by hammering, is made harder.