In the Northern Song Dynasty, there was a famous painter named Wen Tong, who was a master of bamboo painting at that time.
In order to draw bamboo well, Wen Tong keeps drilling in the bamboo forest all the year round, no matter spring, summer, autumn and winter, whether it is windy or rainy, whether it is sunny or cloudy. In dog days, the sun is on fire and the ground is hot. However, Wen Tong still ran to the side of the bamboo forest facing away from the sun, stood in the scorching sun, and watched the changes of bamboo with rapt attention. He measured the length of the bamboo joint with his fingers for a while, and then recorded how dense the bamboo leaves were. Sweat soaked his clothes and his face was sweaty, but he didn't even wipe it with his hands once, as if nothing had happened.
Once, a strong wind blew in the sky. Then, thunder and lightning, a heavy rain is coming. People are running home. Just then, Wen Tong, who was sitting at home, grabbed a straw hat in a hurry, buckled it on his head and ran straight to the bamboo forest on the mountain. Hardly had he stepped out of the gate when the heavy rain began to splash water with the washbasin.
Wen Tong is bent on seeing bamboo in the storm, but he can't slip in the rain! He lifted his robe, climbed the hillside and ran to the bamboo forest. Panting, he ran into the bamboo forest and looked at the bamboo unblinkingly without wiping the rain on his face. I saw bamboo in the wind and rain, bent down and nodded, swaying. Wen Tong carefully kept in mind the posture of bamboo being hit by wind and rain.
Because Wen Tong has made careful observation and research on bamboo for many years, what changes have taken place in the shape of bamboo in spring, summer, autumn and winter? What is the difference between the color and posture of bamboo in rainy and snowy days? What's the difference between bamboo in strong sunlight and bamboo in bright moonlight? He knows exactly what different bamboos look like. So when you draw bamboo, you don't need to sketch at all.
A man named Chao praised Wen Tong and said, Wen Tong already has a plan.
Later, "having a plan in mind" became an idiom, which was used to mean that people made up their minds long before doing anything and had a clear idea in their hearts.