千里送鵝毛

Etymology
or.

According to the Ming scholar, there was a legend that the has once sent an ambassador to  with many tributes including a swan. But on the way, the swan flew away and only a feather was left. Finally, the ambassador gave the feather to the Tang emperor and wrote a poem to explain the incident.

Idiom

 * 1) a trifling present with a weighty thought behind it