Two aboriginal steampunks: 1791, 1847

Soon shall thy arm, UNCONQUERED STEAM! afar
Drag the slow barge, or drive the rapid car;
Or on wide waving wings expanded bear
The flying chariot through the fields of air.
—Fair crews triumphant, leaning from above,
Shall wave their fluttering kerchiefs as they move;
Or warrior bands alarm the gaping crowd,
And armies shrink beneath the shadowy cloud. [1:289]

The optimistic Erasmus Darwin there, from his The Botanic Garden. I particularly like the way the 'fair crews' of pilots and passengers shift into more sinister military oppressors. 1791, ladies and gentlemen.

Fly, puffing and huffing, a half century on.  Here's 'Daedalus Britannicus's Aerial navigation: containing a description of a proposed flying machine on a new principle (1847) (alas not viewable on Google books, presumably because Daedalus Britannicus is still alive and the work therefore still in copyright, grr, grr) but there's a detailed contemporary account of the book here, in an 1864 Athenaeum. A 'Mr Henson' had failed to actualise his steam-powered aerial machine in 1843, despite bringing a bill to Parliament to incorporate 'The Aerial Transit Company'. Steam engines were too heavy to generate the necessary power-to-weight, I suppose. But 'Daedalus Britannicus' had a better idea: 'the moving power being the explosion of mixed hydrogen and air'. This, I feel, could have worked. There's a whole sheaf of possible Steampunk alt-historicals to be written, branching off from this, I'd say.