Inch of Candle
(Sold by). A sale by auction. Instead of the hammer of the auctioneer concluding the bids, the purchaser was the last bidder before the candle went out. Another plan is to stick a pin in a candle, and when the pin drops down, the sale of the article is concluded.
Down were tumbled miracle and martyr, Put up in lots, and sold by inch of candle.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894