Cheng Dawei

Cheng Dawei (程大位, 1533–1606), also known as Da Wei Cheng or Ch’eng Ta-wei, was a Chinese mathematician and writer who was known mainly as the author of Suanfa Tongzong (算法統宗) (General Source of Computational Methods). He has been described as “the most illustrious Chinese arithmetician.”
Almost all that is known about his life is contained in a passage written in the Preface of the book by one of his descendants when the book was being reprinted:

In his youth my ancestor Cheng Da Wei was academically gifted, but although he was well versed in scholarly matters, he continued to carry out his profession as a sincere Local Agent, without becoming a scholar. He never lagged behind either on the classics or on ancient writings with old style characters, but was particularly gifted in arithmetic. In the prime of his life he visited the fairs of Wu and Chu. When he came across books that talked about “square fields” or “grain with the husk removed” … he never looked at the price before purchasing them. He questioned respectable old men who were experienced in the practice of arithmetic and gradually and indefatigably formed his own collection of difficult problems.
Cheng Dawei was not a professional mathematician. From the description cited above, one could deduce that he must have traveled widely. Also must have been well off since he purchased books without asking the price. Again we can see that he was an avid collector of books on mathematics. This is borne out by the contents of his work General Source of Computational Methods which is essentially a compilation of problems from earlier works.