Three feet, one line

For a point on the circumcircle of a triangle, the feet of the perpendiculars dropped from that point to the triangle's three sides (extended if necessary) always lie on a single line. This result is popularly attributed to a Scottish mathematician, but historians have found no evidence he ever wrote about it -- the actual result appears in the work of a different Scottish mathematician, William Wallace. To whom is this line still commonly (if incorrectly) credited?