[Daryl]

Hogan's plane - the pane of glass was just an upper bound under which the club head must remain. In the second pic, you have correctly traced the elbow swing plane in red. But in the last two photos, you have traced the shaft, not the Sweetspot Plane which goes through the ball, and under which the hands lie, and this happens even though he has very high hands through impact. Also, that's not impact in the left photo - his hands move dramatically left at and after impact. There are many rotary swingers who's left wrists are not quite uncocked to the level position and so their hands are much more under the elbow swing plane than Hogan's.

I didn't trace those lines but put perfection aside for a moment and think of the intent. These illustrations were done by others and it was a simple search and find, copy and paste.

I've made BOLD in the quote below, an important point. Also, it may have been widely used in his day but its no longer widely used. There are two versions and as Homer said, its difficult to assign a reference point while using these procedure.

The Club will return appropriately to within a few degrees of the Clubs Lie Angle and as long as this is compensated, it will work.

10-6-D TURNING SHOULDER Locating this Plane Angle reference point geometrically is very involved but seems readily defined from a “mechanical” description. Which is this; the Arms are simply raised and lowered vertically and the Wrists are Cocked and Uncocked with Left Wrist vertical to the ground at all times in a true Single Wrist Action – no Turn or Roll (10-18-C). All this, while the Pivot is imparting the On-Plane motion to the Hands and Arms in both directions. It brings the Hands directly to a Squared Shoulder Plane location. Its Off Plane (Vertical) Loading motion tends to Feel like Clubhead Throwaway but it is the Vertical Left Wrist application of the Golfer’s Flail as shown in Sketch 2-K#5, which insures a positive Downward motion for an effective Three Dimensional Impact.