via: http://www.kameyamado.com/english/how_to_make_tofu.html

Use nigari diluted to 1/5th or 1/6th. Carefully pour into soymilk, stir slowly to thicken. Put through a sieve and set into a square to make “Zaru-Tofu”. If drained of water it becomes real handmade tofu. Adjusting the firmness will affect the solidity, but even if you use a large amount, running it under water will take the nigari out of it. [with pictures]

via: http://www.latimes.com/features/food/la-fo-tofumaking24-2009jun24,0,7809288.story

Note: Adapted from Sona's Kuniko Yagi and Meiji Tofu. Nigari water is a brine used to set the soy milk. It is available at Japanese markets. Serve with grated ginger and soy sauce, or with a chiffonade of herbs, such as shiso or mitsuba, and yuzu. 2 cups cold soy milk (must contain more than 12% soy) 1 teaspoon nigari water 1. In a medium bowl or measuring cup, stir together the soy milk with the nigari water. Pour the liquid into 5 ramekins; each should hold about 3 ounce. 2. Place the ramekins in a stove-top steamer, cover and steam just until the tofu is set on top, 5 to 10 minutes, depending on the heat, type of nigari and soy concentration in the milk. (It will jiggle when tapped, like crème brûlée.) Remove from heat, cool until just warm and serve. Or cool to room temperature and chill; serve within two days.