The following examples do not usually find a place in text-books dealing with involution, and so may be interesting to those teaching the subject. They are simply special cases of the two well-known theorems: (1) that a straight line cuts the six sides of a complete quadrilateral in six points that form an involution, (2) that if any point in the plane of the quadrilateral be joined to the six vertices, the six rays so formed form a pencil in involution.