When can the salt-making process in China be traced back to the earliest?

It can be traced back to the era of the Yellow Emperor. The pre-Qin ancient book "Shi Ben Volume I" said: "In the era of the Yellow Emperor, the princes had the surname of Su Sha, and they began to boil milk in seawater and fry it into salt, with five colors: blue, yellow, white, black and purple." Xu Shen's Shuo Wen Jie Zi in Han Dynasty said: "The ancients cooked sea salt in Su Sha." Su Sha is Su Sha. Bei Tang Shuchao in Shinan of Sui Dynasty quoted Shiben as saying: "The Sha family began to cook the sea as salt, and the sand was the Yellow Emperor." The above records show that it should have happened in the era of Huangdi and Shennong five or six thousand years ago, that is, the beginning of ancient farming life in China.