..please do be careful of Vmcg and Vmca.. totally agree John.
Video etc, you are obviously not old enough to remember the ‘stoneman’ technique.
Test engineer positioned on the centreline at the far end of the runway with a supply of distinctive small stones.
As the aircraft deviates with engine cut, the engineer runs to the side and drops a stone at the point of maximum deviation.
A very good approximation; don't start on one side or the other because the crew could cheat, and don't do this in long grass, or sand / stone desert overruns !
My view of the hilarious procedure was from the safety of the flight deck, excepting a rare view from the grass at the edge of the runway, or of the engineer running for life during a continued take off with limited performance.
From mach 84 in another thread:-
http://www.skybrary.aero/bookshelf/books/3566.pdf