The Ladies' Book of Etiquette, and Manual of Politeness

2. Secondly, when riding with a gentleman, remember that you are best placed on the left side; because in that position the graceful flow of your habit is seen to the greatest advantage, while it does not inconvenience the gentleman by getting entangled with his stirrup, nor does it receive the splashes of his horse. 3. But when you have a double attendance of cavaliers, if you be at all a timid rider, it may become discreet to "pack" you (forgive the homely phrase) between the two, since, in this position, you are the most thoroughly protected from your own horse's shying, or from other horses or vehicles approaching you too closely, being thus forced to take that part of the road to which the better judgment of your companions inevitably guides you. If you be an accomplished equestrian, you will prefer being outside, and (as has been said) to the left. Sit erect in the middle of your saddle, turning your face full towards the head of your horse. Cling as closely as possible to the saddle, but avoid stooping forward, or using your hands to keep you in your seat. Nervous motions on horseback are not only ungraceful, but dangerous, as your horse will not make any allowance for the delicacy of your nerves, and may prove his objections to a jerking hand, or a twitching rein, in a most decided and disagreeable manner.