Full Idea
The proverb says 'Anything fine is difficult'.
Clarification
'Fine' is the Greek word 'kalon', which also translates as 'beautiful'
Gist of Idea
What is fine is always difficult
Source
Plato (Hippias Major [c.382 BCE], 304e)
Book Reference
Plato: 'Early Socratic Dialogues', ed/tr. Saunders,Trevor J [Penguin 1987], p.265
A Reaction
attributed (as usual) to Solon