Green’s Dictionary of Slang

miraculous pitcher (that holds water with the mouth down) n.

the vagina.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1790		‘Bumper Allnight. Esquire’ Honest Fellow 212: Toasts [...] The miraculous pitcher.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1836		‘Toasts’ in New Cockalorum Songster in Spedding & Watt (eds) Bawdy Songbooks (2011) II 30: The miraculous pitcher, that holds water with the mouth downwards.
1838		Crim.-Con. Gaz. 1 Dec. 120/1: Here’s to the down bed of beauty which upraises man, / And beneath the thatch’d house the miraculous can.
1840		[as 1838].