I was recently reading a novella by Brandon Sanderson, the Emperor's Soul, in the postscript he relates a story told to him by a tour guide that a particular Chinese Emperor was particularly fond of carving his own poetry or applying his seal to art he was particularly fond of. Is this true and if so which emperor was it?
I can't say for certain which particular emperor you may be talking about, but engaging with the arts was definitely a popular past time of many emperors (and other nobles).
As with any other culture, the arts were seen as a mixture of both external culture and action, and internal cultivation and personality. China was no different. The elites of dynastic China often engaged in art, poetry, calligraphy, theater, music, etc. The big three for China, of course, being poetry, calligraphy and painting. Emperors, just like other nobles, would have been exposed to such things very early on as part of their cultural education. There were some who took to it with vigor.
Emperor Xuanzong of the Tang Dynasty was known as a supporter of the arts and literature and his reign (713 - 756 AD) was a truly enormous time for Chinese arts and literature. Many of China's most famous poets, including Li Bai and Du Fu, and artists lived during this time. Xuanzong's most well known contribution to the field is a poem that's in Three Hundred Tang Poems (唐诗三百首). More interestingly, there's a set of poems by Xuanzong that are attached to a treatise on Daoist swords and mirrors that was given to him by Sima Chengzhen, the patriarch of the Shangqing school of Daoism (上清含象剑鉴图).
Emperor Huizong of the Song was particularly renowned for his engagement with the arts (and might be who the tour guide was referring to). Aside from his major patronage of the arts, he made a number of paintings during his lifetime and his calligraphy was very highly praised. Patricia Ebrey has a really big book on him titled Emperor Huizong.
If you're interested more in the artistry and elites of dynastic China, check out these books:
Bol, Peter K. “This Culture of Ours”: Intellectual Transitions in T’ang and Sung China. Stanford: Stanford University Press, 1992.
Chiang, Yee. Chinese Calligraphy: An Introduction to its Aesthetic and Technique. Cambridge: Harvard University Press, 1973.
Holcombe, Charles. In the Shadow of the Han: Literati Thought and Society at the Beginning of the Southern Dynasties. Honolulu: University of Hawai’i Press, 1994.
Lewis, Mark Edward. China’s Cosmopolitan Empire: The Tang Dynasty. Cambridge: The Belknap Press of Harvard University Press, 2009.
McNair, Amy. The Upright Brush: Yan Zhenqing’s Calligraphy and Song Dynasty Politics. Honolulu: University of Hawai’i Press, 1998.
Owen, Stephen. The Great Age of Chinese Poetry: The High T’ang. New Haven: Yale University Press, 1981.
Sullivan, Michael. Chinese Landscape Painting. Berkeley: University of California Press, 1980.
Many Chinese emperors are good poet. One of the more famous poetic emperor was Huizong who is not only a great poet but also a tea master, a master painter and a great musician who can play ancient instrument. He happened to be good at everything except being emperor. Another famous one is Li Yu who is very similar to Huizong that he's a mastergrade painter, musician and poet. Both of them also bad at being ruler and bombed their own kingdom. These two also shared a fact that the poems they wrote after they have been captured by enemies are very sad.