挥翰临池

Explanation: John: Toba, by means brush; pond: refers to the writing. Refers to the writing brush. 　　Source: Jin Wei Heng, "book four-body potential" that the Eastern Han Dynasty, Zhang Zhi pond practicing calligraphy, water to make black. " 　　Examples: ~, Natural and so Gong Fu unmatched. (Qing Zeng Pu, "Flower" The fifth round)