Hong-wu: Year 9, Month 5, Day 1
19 May 1376
The Grand Master for Thorough Counsel Li Ya-fu and others who had been sent by Chen Tuan of Annam came to Court and offered tribute of local products. The Emperor spoke to the officials of the Secretariat, saying: "The various yi are separated from us by mountain and seas. If the frequency at which they come to Court to offer tribute is not stipulated, it will cause great trouble to these distant people and they will not be at ease. Last year, Annam came and requested that the frequency for coming to Court and offering tribute be stipulated. They were instructed to accord with ancient practices and either come once every three years or just once every reign (或世見). Now, another envoy has arrived. This is pointless in the extreme. Instruct them again of my wishes. The fan and yi countries should observe the regular principles and come to offer tribute once every three years. They should not come more frequently and the number of envoys accompanying the mission to Court should not exceed three to five. The goods offered as tribute need not be excessively valuable, as long as they manifest the loyalty and respect of those who offer them.
Zhong-yang Yan-jiu yuan Ming Shi-lu, volume 4, page 1763