《礼记·礼器》
其余的贡品没有固定的品种，原则上是你这个诸侯国有什么土特产你就贡献什么，这表示再遥远的东西天子也能得到。
其出也，肆夏而送之，盖重礼也。
The remaining offerings had no prescribed types; in principle, each feudal state contributed whatever special products it had, implying that the emperor could obtain even the most distant items.