The emperor also made a deliberate decision on the matter of establishing a crown prince, because after being made a crown prince, it means that if you do not make any mistakes of principle, there is a great possibility that the future throne will be yours. And the emperor was a high power in ancient times, how many people faced such a great power and did not move, so the struggle for the imperial throne over the years was the most tragic, not only the concubines fought with each other, but also the courtiers took sides early.
After Yongzheng ascended to the throne, he had a total of 10 sons, either prematurely or young, so only three princes could take on the big responsibility. Among the three sons, only Hongli was young and old, not only did Kangxi like him, but this son also helped himself become emperor, so he was the most suitable person. In Yongzheng's heart, he was also very optimistic about Hongli, but he still wanted to pass the test to examine him.
I believe that many people are not unfamiliar with the story of "Nine Sons And Nine Sons", "Nine Sons and Nine Sons" is also a more cruel process, the Yongzheng Emperor also has a deep understanding of this, so he wants to change to prevent the occurrence of tragedies, so he abandoned the original system of establishing a prince, and established a secret crown prince, that is, the future monarch will be born from the prince. Then there will be some tests for the princes to test whether they can become a good monarch in the end, so Yongzheng tested the Hongli with a piece of fat boiled in white water, and the Hongli also passed the test and became the crown prince.
In feudal society, the gizzard meat was given the blessing of the gods, and it was a great honor to receive such a piece of meat in the sacrifice, which was both a test and an expectation for the Hongli calendar, and thus made Yongzheng firmly establish the Hongli as the heir, and later made him the crown prince. And the Hongli did not disappoint Yongzheng, in the hands of Qianlong, the Qing Dynasty reached its peak period, first, because of the accumulation of the previous two emperors, and second, because of Qianlong's own ability to govern. Qianlong was the longest-reigning emperor and the emperor with the best luck, with a smooth life and a strong body.