Lucian, The Ignorant Book Collector
4 (tr. H.W. and F.G. Fowler):
An ape is still an ape, says the proverb, though his trappings be of gold.
πίθηκος γὰρ ὁ πίθηκος, ἡ παροιμία φησί, κἂν χρύσεα ἔχῃ σύμβολα.
Claudian, Against Eutropius
1.303-306 (tr. Maurice Platnauer):
'Twas as though an ape, man's imitator, had been decked out in sport with precious silken garments by a boy who had left his back and quarters uncovered to amuse the guests at supper.
humani qualis simulator simius oris,
quem puer adridens pretioso stamine Serum
velavit nudasque nates ac terga reliquit,
Aunque la mona se vista de seda, mona se queda.
Although the monkey dresses in silk, she remains a monkey.
Erasmus, Praise of Folly
According to the proverb of the Greeks, an ape is always an ape, even if it's dressed in purple.
iuxta Graecorum proverbium, simia semper est simia, etiam si purpura vestiatur.