A focus timer for iPhone. Water gathers in a bamboo tube in an ink-painted garden, and every half minute the tube tips, pours and knocks — so you always know the session is still running without looking up.
Twenty-five minutes is hard to feel, so you check. And the more you watch a number count down, the more the time is on your mind. Shishi doesn't show you a number. It lets you hear one.
The sound is small; it won't stop your hands. Time stops being something you check and becomes something in the room with you. That is what a shishi-odoshi has always been for.
Only the end is unmistakable. The last knock is louder, and you feel it in your hand.
The tipping is the weight of the water against the balance of the tube. A brim-full tube only just outweighs its own tail, so it goes over reluctantly, then whips as the water runs to the low end, and comes back faster than it went — empty and light. It is never quite the same twice, and it often knocks twice.