I've been going to some really fascinating talks at the University of Washington. Week after week the Chinese Studies department has been hosting brilliant scholars who are doing research regarding some aspect of tea. Recently there was a lecture on the history of "talking about tea" which Dr. James Benn has traced through its origins in the writings of Tang poets. For a thorough treatment of the subject see his book "Tea in China: A Religious and Cultural History" http://www.uhpress.hawaii.edu/p-9322-9780824839642.aspx
Dr. Benn made a point to emphasize the rapid onset and dissemination of tea drinking in China. We know that tea wasn't as ancient a beverage as Chinese civilization itself, it was probably first consumed for its medicinal properties around early Tang times. But from the time when celebrity poets of the Tang were introducing the brewed/steeped/whipped beverage to the literate elite to the implementation of a market tax for tea sold and consumed by common people was incredibly short. Lu Yu's classic of tea was making its rounds in the mid 8th century, and the tax was implemented by the central government in 780 or thereabouts.
To understand the literary mention of tea in Tang Dynasty China, one has to first understand the basic function of literature at the time. I'll try to be brief: All educated people were well read in the 'classics', a group of texts and their commentaries which were written mostly during the benevolent and properly Confucian Zhou Dynastic period. Being educated meant being familiar with the classics to the point of having them memorized backwards, forwards, up, down and sideways. The poets of the time were not praised for their unique and experimental use of language, but for their brilliant transmission of what had already been stated in the classics. There was a canonical way of talking about most anything a Chinese poet might want to talk about. But the classics hadn't any mention of tea. So poets who were moved to include tea in their work had to find novel ways to incorporate this new beverage into their vocabulary. Li Bo and Li Hua both talked about it as a Daoist elixir of immortality, alluding to mica (used in alchemical immortality elixir) and the saliva production site beneath the tongue (which is key to Daoist meditation practices which lengthen ones life).
Jiao Ran, a poet friend of our man Lu Yu, waxed spiritual about teas ability to raise one to the gods and compared tea to alcohol. In his comparison, he sneers at earlier Daoist poet Tao Qian's use of wine. Jiao Ran made an interesting choice here to compare these two beverages. It was a natural choice because of the ritual context and frequency of wine in the 'Classic of Odes' which he was drawing from. There was already a way to talk about wine, another psychoactive beverage, in the annals of the classics. It also marked, though, a switch of China's 'drug of choice'. I like to think of this switch as parallel to the European switch from beer to coffee which coincided with the Renaissance.
There was quite a lot of compelling content in Dr. Benn's lecture, but I'll leave it to you to go out and buy his book. I get rambly at the intersection of strong Tie Guanyin and fascinating Chinese Tea research. And I'm on my fourth pot of the day.