QUOTES BY FRANCOIS DE LA GUÉRINIÈRE
On Training

"There are two ways of giving with the hand. The first, which is the more common and most frequently used, is to lower the bridle-hand, as we have indicated. The second way is to take the reins in the right hand, behind the left hand, and while slightly raising the reins in the left hand, pass control to the right hand, and finally, giving up control with the left hand completely, lower the right hand onto the neck of the horse, and hence the horse finds itself completely free from contact. This manner of giving with the hand is called descente de main: it is also performed by taking the ends of the reins with the right hand, held at the height of the rider's head, the arm straight out and free; but you must be quite sure of the horse's mouth and its readiness to obey, in order to use this method. Care must be take not to give with the hand or perform descente de main when the horse's weight is on its shoulders: the proper time to perform this movement is after a half-halt, and when you feel the horse coming back on its haunches, give with the hand or perform the descente de main. The proper moment, difficult to discern and seize, is one of the most subtle and useful aids of horsemanship; for the horse, bending its haunches just as contact is released, must necessarily remain light in hand, having no other support for the head." ("Ecole de Cavalerie")