Japanese for "Japanese poem", waka predates even
haiku and was the favoured style of
court poetry from the 6th to 14th centuries.
Murasaki Shikibu was famous for her waka, amongst her other writings. The pattern of syllables are as follows:
Choka "Long poem" (5-7 ad infinitum...7)
Tanka "Short poem" (5-7-5-7-7)
Haiku (5-7-5)
The term "tanka" was only used from the Meiji era onwards, in the 19th century, to distinguish it from the earlier, classical waka. In addition, tanka poetry does not include the longer "choka", "sedoka" and other variations. The Emperor Meiji wrote waka, as did his wife the Empress Shoken. The following is a waka written by the Emperor Meiji on the matter of brotherhood.
It is our hope
That all the world's oceans
Be joined in peace,
So why do the winds and waves
Now rise up in angry rage?
Sources
http://www.threshold.ca/reiki/japan/gyosei_waka_poetry.html
http://www.asahi-net.or.jp/~EA8T-MNK/english.html