有一年夏天，曹操率領部隊去討伐張繡，天氣熱得出奇，驕陽似火，天上一絲云彩也沒有，部隊在彎彎曲曲的山道上行走，兩邊密密的樹木和被陽光曬得滾燙的山石，讓人透不過氣來。到了中午時分，士兵的衣服都濕透了，行軍的速度也慢下來，有幾個體弱的士兵竟暈倒在路邊。
曹操看行軍的速度越來越慢，擔心貽誤戰機，心里很是著急。可是，眼下幾萬人馬連水都喝不上，又怎么能加快速度呢？他立刻叫來向導，悄悄問他：“這附近可有水源？”向導搖搖頭說：“泉水在山谷的那一邊，要繞道過去還有很遠的路程。”曹操想了一下說，“不行，時間來不及。”他看了看前邊的樹林，沉思了一會兒，對向導說：“你什么也別說，我來想辦法。”他知道此刻即使下命令要求部隊加快速度也無濟于事。腦筋一轉，辦法來了，他一夾馬肚子，快速趕到隊伍前面，用馬鞭指著前方說：“士兵們，我知道前面有一大片梅林，那里的梅子又大又好吃，我們快點趕路，繞過這個山丘就到梅林了！”士兵們一聽，仿佛已經吃到嘴里，精神大振，步伐不由得加快了許多。
故事出自《世說新語·假譎》。成語“望梅止渴”，比喻用空想安慰自己或他人。
quenching thirst by watching plumscao cao of the three kingdoms period (220-265) was not only a capable politician in managing state affairs, but also a strategist good at leading troops in going to war.
one summer, cao cao was leading his troops in a punitive expedition against zhang xiu. it was extraordinarily hot. the burning sun was like a fire, and the sky was cloudless. the soldiers were walking on the winding mountain paths. the dense forest and the hot rocks exposed to the sun on both sides of the paths made the soldiers feel suffocated. by noontime the soldiers' clothes were wet through with sweat, and the marching speed slowed down. some solders of weak physique even fainted on the roadside.
seeing that the marching speed was slower and slower, cao cao was very worried because he feared that he might bungle the chance of winning the battle. but how could they quicken their speed? cao cao at once callde the guide and asked him on the quiet whether there was a source of water nearby. the guide shook his head, saying that the spring water was on the other side of the mountain, which was very far to have to make a detour to reach. cao cao realized that time didn't permit them to make such a detour. after thinking for a moment, he said to the guide, "keep quiet. i'll find a way out." he knew that it would be to no avail to order his troops to quicken the steps. he had a brain wave and found a good solution. he spurred his horse and came to the head of the column. pointing his horsewhip to the front, cao cao said, "soldiers, i know there is a big forest of plums ahead. the plums there are both big and delicious. let's hurry along, and we will reach the forest of plums after bypassing this hill." when the solders heard this, they immediately slobbered. picturing in their minds the sweet and sour flavour of the plums, the soldiers felt as if they were actually eating the plums, the soldiers felt as if they were actually eating the plums themselves. the morale greatly boosted, the soldiers quickened their steps a great deal automatically.
this story comes from "the fake tangery" in anecdotes of this world by liu yiqing of the southern dynasties period (420-589). from this story, people have derived the set phrase "quenching thirst by watching plums" to refer to trying to comfort oneself of others by idle dreams.