I was amused by this 1900 U.S. census record of my 2nd great grandparents Aeneas V. Graham and his wife, Amanda P. Underwood (Graham) in their old age. 
The part that brought a smile was the enumerator's recording of the occupation details (below). The left column is for "Trade or profession or particular kind of work"; the right hand column is for "General nature of industry, business, or establishment in which this person works, as cotton mill, dry goods store, farm, etc."
So for Aeneas, his occupation (left column) was Retired. So far so good.
The "General nature" of his industry or business (right column) was old age. I didn't know old age was a business or industry!
1. 1910 U.S. census, Washington County, Pennsylvania, population schedule, Monongahela City, p. 191 (stamped), Enumeration District (ED) 212, sheet 12 A, dwelling 200, family 201, A V Graham; Ancestry.com (https://www.ancestry.com : accessed 3 February 2018); citing NARA microfilm publication T624, roll 1426.