Students of Japanese are quite used to characters (漢字) nearly always having multiple pronunciations, ranging from one syllable to five or more. (Example: in Japanese, depending on the context, the character 侍 can be pronounced as ジ or as さむらい.)
That’s one of the areas in which switching from studying Japanese to studying Chinese came as a relief: in Chinese you can be sure each hanzi (Chinese character) has a monosyllabic reading, and 90% of characters have only one reading.
In my studies, I recently discovered that this has not always been the case. My Chinese textbook gives me three examples that were around until 1977, when a character reform had them eradicated.
– 瓩 qiānwǎ (kilowatt); now standardized as 千瓦
– 浬 hǎilǐ (nautical mile); now standardized as 海里
– 呎 yīngchǐ (foot); now standardized as 英尺
Besides their very existence, I found several things about these characters interesting. First, they’re all for units of measure. Maybe at one point people liked the idea of a single character for each unit of measure? Second, it was an interesting evolutionary turn the language was taking. From a student’s perspective, I’m not sure I like it, but it’s interesting. You can clearly see which part in each character represents which syllable. Lastly, it was the government that quashed this fairly recent orthographic innovation in favor of standardization.
Note: You won’t find this info in Wenlin. I got it from 现代汉语 (上海教育出版社, 2004).
2011 Update: The venerable scholar Victor Mair writes about this subject on Language Log: Polysyllabic characters in Chinese writing.