A barley corn is better than a diamond to a cock.
The source for the proverb is English Proverbs and Proverbial Phrases by William Carew Hazlitt (Google Books). The poster is made with AutoMotivator. The image is from Steinhowel's Aesop at Flickr. The proverb provides a specific interpretation of the famous Aesop's fable of the rooster who is frustrated when he finds a diamond in his manure heap, rather than a barleycorn. Is the rooster just being practical (he can eat a barleycorn, not a diamond), or is he a fool who doesn't recognize a good thing when he sees it? You can find the fable interpreted both ways - this proverb offers the very practical interpretation, recognizing the rooster as wise.