The Chinese couplet form is more tightly restrained than in English; these restrictions include: 豫章故郡， 洪都新府。 星分翼軫 ， 地接衡廬。 "Formerly Yuzhang Commandery, Currently Hongdu Prefecture.
Among stars, it separates the Wings and Chariot Constellations, On the ground, it abuts the Heng and Lu Mountains..." At the same time, the use of uncommon words and allusions to literary or historical events was also emphasised.
Li Si's Jianzhuke Shu (Petition against the Expulsion of Guest-officers), from the Warring States period, also contained couplets.
[3] A renowned pianwen essay is the Tengwang Ge Xu, written by the early Tang dynasty poet Wang Bo; by the mid-Tang, however, the Classical Prose Movement headed by Han Yu and Liu Zongyuan challenged the pianwen form, advocating a return to the freer, more direct and less restrained prose that prevailed in pre-imperial times.
The characteristics of vernacular Chinese, where many words are formed from more than one character, make it almost impossible to write the strictly parallel couplets demanded by pianwen.