|An 1680 version of the Papin's digester, built by Denis Papin, from Robert Thurston's A History of the Growth of the Steam-Engine (1878). |
In 1679, French engineer Denis Papin invented what he called a "digester or engine for softning bones", aka "bone digester", or Papin's digester as it later came to be called.  The following is a 1681 version of the details of the digester: (Ѻ)
Early versions resulted in explosion, owing to the extreme pressures. Late version fixed this problem by adding on steam release valve.
It is said that by watching the steam release valve bob up and down that Papin conceived of the design of the steam engine, the Papin engine, as outlined in his 1690 memoir "A New Method to Obtain Very Great Motive Powers at Small Cost." 
The following are related quotes:
“I went this afternoon with several of the Royal Society to a supper which was all dressed, both fish and flesh, in Monsieur Papin’s digestors, by which the hardest bones of beef itself, and mutton, were made as soft as cheese.”— John Evelyn (1682), diary note, Apr 12 
● Timeline of engine development
1. Papin, Denis. (1681). A New Digester or Engine for Softning Bones: Containing the Description of Its Make and Use in These Particulars : Viz, Cookery, Voyages at Sea, Confectionary, Making of Drinks, Chymistry, and Dying. With an Account of the Price a Good Big Engine Will Cost, and of the Profit it Will Afford. Mallinckrodt Chemical Works.
2. (a) Papin, Denis. (1690). “A New Way to Obtain Very Great Motive Powers at Small Cost” (Nova Methodus ad Vires Motrices Validissimas levi Pretio Comparandas). Acta Eruditorum, anno, Aug., pgs. 410-14.
(b) Muirhead, James. (1859). The Life of James Watt, (English translation: Ch. XI, Denys Pain: His memoir of 1690, Section: A New Way to Obtain Very Great Motive Powers at Small Cost”, pgs. 131-42). London: John Murray.
3. Thurston, Robert H. (1878). A History of the Growth of the Steam-Engine (Ѻ). D. Appleton and Co., 1886.
4. Anon. (2012). Engineers: From the Great Pyramids to the Pioneers of Space Travel (§: Denis Papin, pgs. 106-107). DK Publishing.
● Steam digester – Wikipedia.