OSAKA -- A 53-year-old civil servant in Osaka Prefecture who has been researching the history of toilets in Japan for more than 30 years has published his latest findings in what he calls "The Journal of Toilet Culture."

The publication is the third such venture for Shigenori Yamaji of Toyono, Osaka Prefecture, following his "Toilet Archaeology" and "Notes on the Toilet."

Yamaji's latest work, a 216-page volume, covers toilets and toilet usage in Japanese society, from aristocrats in the Heian Period (8th to 12th century) to commoners in the Edo Period (17th to 19th century). "When I look at toilets, the lives of people in the past and the present come alive," said Yamaji.

He described his research as an interdisciplinary study of human beings.

Yamaji draws on quotations from classic works of Japanese literature such as the "Konjaku Monogatari" ("Stories, Ancient and Modern") and the "Uji Shui Monogatari" ("Selections from Uji Tales").

He has also established historical details such as the fact that the Heian nobility used a portable toilet known as "omaru," and that toilet covers differed in style during the Edo Period.

Modern works of literature by Ryunosuke Akutagawa and Yojiro Ishizaka have also led him to findings about toilets in the early part of the 20th century, such as the introduction of flush toilets and the linguistic origin of the word "kawaya," an archaic word for toilet.

Yamaji's work is also illustrated with photographs of unusual toilets he discovered while traveling in China and his reflections while using an "open-air toilet" that barely had a partition.