From
世说新语·
方正 — a young Wang Xianzhi (
王献之, Wáng Xiànzhī) watched players over their shoulders and was scolded: '
管中窥豹,
时见一斑' (gazing at a leopard through a tube, one only sees a single spot).
全豹 ('the whole leopard') is the contrast — seeing the entire animal, the complete picture.