Taken from: Paul Wheatley: Geographical notes on some commodities involved in sung maritime trade.

Empress Liu Kuei-fei (1) refused to pay the very high sum of 30,000 strings of cash demanded by a foreign merchant for two-tenths of an ounce of ambergris.

Note: All authors agree that the Chinese only got to know Ambergris through the Arabs and that they were unaware that the substance was also found on their own coast. The Arabs collected Ambergris on all Indian Ocean coasts (including East-Africa); but the importance of early texts pointing to Ambergris in China is also that we have mentions of  black people arriving in China at the same time as the Ambergris; the Arabs were also importing black slaves, (who might also have come from South East Asia and / or Africa)

(1) Liu Kuei-fei: concubine of the Emperor Kao - tsung , who died in 1187.