All 5 Uses of

subtle
in
The Iliad by Homer (translated by: Lang, Leaf, & Myers)

But now let us bethink us of battle with all speed; this is no time to dally here with subtleties, for a great work is yet undone.†
Book 19 *

subtleties = things that are not obvious, but noticeable by someone with adequate sensitivity and relevant knowledge

And to him in subtlety queen Hera spake: 'Though wilt play the cheat and not accomplish thy word.†
Book 19

So spake she, and Zeus no wise perceived her subtlety but sware a mighty oath, and therewith was he sore blinded.†
Book 19 *

For on this side and on that the gods went forth to war: to the company of the ships went Hera, and Pallas Athene, and Poseidon, Earth-enfolder, and the Helper Hermes, pro-eminent in subtle thoughts; and with these went Hephaistos in the greatness of his strength, halting, but his shrunk legs moved nimbly under him: but to the Trojans went Ares of the glancing helm, and with him Phoebus of the unshorn hair, and archer Artemis, and Leto and Xanthos and laughter-loving Aphrodite.†
Book 20

Definitions:

(1) (subtle as in: a subtle poison)
working in an indirect or hidden way
(2) (subtle as in: a subtle shade of blue)
understated so as not to draw excess attention
(3) (subtle as in: a subtle difference or thinker)
not obvious, but noticeable with enough insight and knowledge

or:

able to notice or understand things that require insight and sensitivity