The Japanese, like the Chinese, used graded joss sticks as the basic method of incense timekeeping; the charge for a geisha's time was in terms of half-hour incense sticks. Incense seals in Japan were solid cubes of hardwood with the seal character carved into the top in a square groove to a depth and width of 1/4in. Powdered incense was placed in the groove and burned along it. The Ji Koban was essentially a large free-standing incense trail in a wooden container with time plates of various materials inserted at regular intervals to mark the hours. The Koban Dokei, in principle, was the same as the Chinese seals or the Ji Koban. A trail of incense was laid out on a bed of ash in a container; in this case the grid was a simple one that rotated a quarter turn, four times, so the seal formed was that for the 'heart of Buddha'. Small hour markers were laid out at intervals and timekeeping proceeded with the burning of the incense.