From
The Complete Golfer (1905) by
Harry Vardon.
Open Champion, 1896, 1898, 1899, 1903.
American Champion, 1900.
"The head should be kept perfectly motionless from the time of the address until the ball has been sent away and is well on its flight. The least deviation from this rule means a proportionate danger of disaster.
When a drive has been badly foozled, the readiest and most usual explanation is that the eye has been taken off the ball, and the wise old men who have been watching shake their heads solemnly, and utter that parrot-cry of the links, "Keep your eye on the ball." Certainly this is a good and neccessary rule so far as it goes; but I do not believe that one drive in a hundred is missed because the eye has not been kept on the ball.
On the other hand, I believe that one of the most fruitful causes of failure with the tee shot is the moving of the head. Until the ball has gone, it should, as I say, be as nearly perfectly still as possible, and I would have written that it should not be moved to the extent of a sixteeenth of an inch, but for the fact that it is not human to be so still, and golf is always inclined to the human side."
But, if you want, go ahead and move your head.
Back and forth.
Or up and down.
Or -- double your pleasure -- do both!
Or neither.
Your call.