An ordinary-sized drink of liquor.

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1836.  The thimble conjurer having asked the barkeeper how much was to pay, was told that there were sixteen smallers, which amounted to one dollar.—‘Col. Crockett in Texas,’ p. 83 (Phila.).

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1842.  Every puppy that would be keeled over with a smaller of rum and ’lasses turns up his nose at him.—Phila. Spirit of the Times, Jan. 3.

3