oncer

On whatever point Jane’s eyes rested, through whichever line her gaze ran, she saw cheques being signed, credit-card counterfoils being scrawled across, standing orders being arranged, and cash – wholesome dosh, ponies, monkies, oncers, coins of the realm – flowing around like mercury, like some element.

Could he but once see Nature as / In truth she is for ever, / What oncer would not fall in love?