In Lu Xun's famous novel "The True Biography of Ah Q", the judge at that time, after convicting Ah Q, asked him to sign the painting, he originally wanted to use a brush to draw a circle, but he did not pay attention to draw the shape of a melon seed. In fact, for a long time in ancient China, the contracts of the ancient people used "painting" as a signature, because the literacy rate of the ancient Chinese people was very low. Then everyone may have a question in their minds: Drawing a circle on paper is not an easy task? Why did the ancient people use this method as a signature, and were they not afraid of being used fraudulently?
This has to start with the history of signing and painting. According to ancient historical records, the signature painting should have originated in the Tang Dynasty, at that time, if you left your own personal notes on documents, calligraphy and paintings or contracts, this would be called "pledge", equivalent to the current "signature" and "signature". At that time, in addition to the prohibition of cursive writing for the emperor, other contracts and documents generally used a variety of fancy and personalized cursive, and these signatures were collectively called "flower pledges".
In the Song Dynasty, when the officials of the Song Dynasty wrote official documents, they generally only wrote their own names at the end of the documents, so they were also called "pledge characters". For example, Wang Anshi, the famous prime minister of the Song Dynasty, wrote the word "stone" in his signature, and only one stroke and one take, directly omitting the following "mouth" character. Later, some officials commented that his signature looked like an "anti" word, so he added a circle in the middle to replace the word "mouth".
So the question is, most of the people at that time were illiterate, if they needed to sign, what should they do? Therefore, many people have a clever move, so that the people directly imitate Wang Anshi and directly draw a circle instead, which is the origin of the so-called "painting pledge". In fact, when painting the pledge, the government usually needs the people to press their own handprints as auxiliary evidence, so the painting itself may only be a symbolic meaning.
On the other hand, because many ordinary people are new to brushes, it is very difficult to draw a complete circle, so the patterns they draw have certain particularities. For example, Ah Q wanted to draw a circle, but it turned out to be a melon seed shape, so in fact, the painting itself also has a special meaning of identifying ordinary people.