100 degrees Celsius or Try Telling My Wife

"Count Rumford has taken much pain to impress on the minds of those who exercise the culinary art, the following simple, but practical, important fact, namely; that when water begins only to be agitated by the heat of the fire, it is incapable of being made hotter, and that the violent ebullition is nothing more than an unprofitable dissipation of water, in the form of steam, and a considerable waste of fuel ... it is not by the bubbling up, or violent boiling, as it is called, of the water that culinary operations are expedited."

Quoted from Culinary Chemistry, 1821 in Alan Davidson's North Atlantic Seafood.

I might also try and tell Nanda to soak kidney beans overnight!