Sentence:  While we boast of our farming, we must repeat again and again, the secret of our prosperity. It is a regular rotation of crops, making a little out of many articles, rather than attempting to make much of one; remembering the Scotch proverb, that "many a <WSD>mickle</WSD> makes a muckle"; ... 
Meaning of the word marked with <WSD> tags:  A small amount.