The earliest letters home are on exhibit at the Yunmeng Xiangshan Museum in Xiaogan, Hubei province, Nov 2, 2014. [Photo/IC]

The two letters, inscribed on wooden tablets, were unearthed in the west suburb of Yunmeng county of Hubei province in December 1975. The letters are from the end of the Warring States period, which date back over 2,200 years ago, and are said to be the oldest letters home in the world.

The letters were written by brother soldiers Heifu and Jing from the Qin army in today's Huaiyang, Henan province, to their brother at home "Zhong". The letters are now well preserved and the ink handwriting is still clear and recognizable.

From the two letters, we can learn about social and economic development during that period. According to experts, the letters were delivered home by acquaintances, as a way of delivering personal letters through official mail was still not allowed at the time. It wasn't until the Song Dynasty that the delivery of personal letters was permitted.

Also, the format of writing a letter was not quite the same as that in China today. For example, the date was written at the beginning of the letter, instead of at the end. Some vocabulary in the letters are still in use today in Chinese letters.