Cóng tā de yántánjǔzhǐ kějiàn-yībān, zhè rén hěn yǒu jiàoyǎng.
From his speech and manners you can get a glimpse - this person is quite refined.
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history
From 《世说新语·方正》: a young Wang Xianzhi was dismissed by his elders with 此郎亦管中窥豹, 时见一斑 - 'this boy looks at a leopard through a tube, seeing only one spot.' The 一斑 (one spot) became shorthand for a revealing fragment.
usage
Typically at the end of a sentence: 'X 可见一斑' or 'X 由此可见一斑' = 'X can be glimpsed from this.' Presents a small piece of evidence as sufficient indication of a larger reality.