...the length of a man's arm from the elbow to the extremity of the middle finger. The cubit among the ancients was of a different length among different nations. Dr. Arbuthnot states the Roman cubit at 17 inches and four tenths; the cubit of the scriptures at a little less than 22 inches; and the English cubit at 18 inches.
Webster's 1828

Which of you by taking thought can add one cubit unto his stature? And why take ye thought for raiment? Consider the lilies of the field, how they grow; they toil not, neither do they spin: And yet I say unto you, That even Solomon in all his glory was not arrayed like one of these.
Matthew 6:27-29