Using data Japanese and Chinese historical documents，we can reconstruct the trading activities of
Imperial Household Department merchant，Zhang Dingchen with Japan during the summer of 1700． This
date reveals that the profit from the trade，which exchanged raw silk and white sugar for Japanese copper，
were much more than 30% reported to the Emperor Kangxi． Actually，the large profit was hidden． In
fact，the copper would bring higher return，which was stable and long-term，to the “Imperial Merchant”
from 1700-1715，as long as the supply of the copper in Japan did not decline sharply．