[header] How to make rat poison [title] Mix a 1/4 pound (113 g) of plaster of paris with 1/4 pound (113 g) of cornmeal in a large bowl. [substeps] Plaster of paris can be bought at most craft stores and hardware stores. It is a dry powder made of gypsum that, when mixed with a liquid, thickens and eventually hardens. 
[title] Add 1-2 cups (0.2 l to 0.47 l) of milk. [substeps] You can add more milk if clumps of the cornmeal or plaster of paris are still dry.