It does not look very comfortable. Sitting astride dates back to antiquity according to Wikipedia and developed in European countries in the Middle Ages as a way for women in skirts to ride a horse in modest fashion while also wearing fine clothing.
Today we have side saddle classes at the finest horse shows: Devon, Upperville, and Washington International, among others. You also see people riding "aside" in the hunt field.
English sidesaddle classes today are based on the norms established in the hunt field from 100 years ago. The class is judged rigidly and perfection is paramount. You must wear the appropriate dress, have the right appointments, tack, horse and style. Turnout is extremely important.
This is what a sidesaddle looks like, this one is Hermes.
Below are the rules from 2002, from the International Sidesaddle Organization for Hunter Class Appointments. You'll see below that the rules are rather strict and detailed. I have seen judges actually pull out the sandwiches from the sandwich case and check them to see if they are fresh. If I am not mistaken, the bread must not have heels on it (not sure if I said that correctly). Talk about attention to detail!
Section 5.2.2 – Hunter Class Appointments. See Pertinent USA Equestrian Rules.
Ladies’ Hunter Under Side-Saddle. May be held with or without appointments; however, the prize list must specify if appointments are required. Proper appointments are as follows:
- Hat – Black hunting silk top hat, crown at least 4-1/2” high, or bowler.
- Veil – Optional. If worn, must be traditional black and fit securely over hat brim and under chin.
- Neckwear – Plain white hunting stock neatly tied and fastened with a plain gold safety pin. Pin should be horizontal.
- Habit – Melton or other cloth of black or dark blue color, unless bona fide hunt member of a recognized hunt whose livery color is different; then hunt livery color with hunt colors is permissible. Lining must match.
- Breeches – Same color as habit (Need not be of same material.)
- Collar – Same material and color as coat unless members has been invited to wear the hunt colors, in which case, the color should conform to the livery of the hunt and be worn only on coats of the hunt livery color.
- Vest – Of plain white, buff or yellow material.
- Buttons – Must conform to hunt livery. Usual specifications are: Brass or bone on vest. Black bone on coat. If member has been invited to wear the hunt button, should be engraved with the hunt emblem, otherwise should be plain.
- Boots – Black, without tops, of plain black calf without tabs. Boot garters, if worn, plain black.
- Spur – Optional, if worn, must be regular hunting spur without rowels, worn high on the heel.
- Whip – Light hunting whip with thong and lash, required.
- Gloves – Brown leather gloves or heavy wash leather.
- Rain Gloves – White, canary or buff rain gloves. Should be carried fingers forward on off (right) side under billets and just showing in front of saddle flap with the thumbs facing upward.
- Jewelry – Except for stock pins, finger rings and small plain stud earrings for pierced ears, jewelry is not permitted.
- Hair – With hair net, preferably in but. Must be neat and unobtrusive, and must not touch collar.
- Safety Helmets are required in over fences classes.
- Sandwich case – Must be combined sandwich case and flask. Sandwich case must contain a sandwich, wrapped, and flask must contain sherry or tea.
- Bridle – Must be either double or Pelham. All leather must be flat. A caveson noseband must be used. Rubber reins are not permissible. Bridle and reins may be sewn to bit(s).
- Breastplate – Flat leather is optional but preferred.
- Martingales – Not permitted, except in classes over fences.
- Saddles – Must be of plain English type. May have suede seat and pommels. Lining may be leather or linen. Numnahs and saddle cloths not permitted.
- Girths – Three fold leather or Fitzwilliam. No elastic permitted. Cannot be shaped. Balance girth necessary.
- Iron – Should be regular side-saddle iron with oval eye, or safety stirrup. Should be large, workmanlike and polished without pads.
Judges should give particular attention to quality, condition and cleanliness of tack.
I also love this photo from Wikipedia, from Australia. That is one high jump, I am impressed that this rider could do this sidesaddle. Don't try this at home!
In certain parts of the US sidesaddle has gotten popular. Here in Virginia there are lots of shows that offer sidesaddle and up around Middleburg, Virginia (near Washington) there are many places to learn to ride sidesaddle. You need a special horse with a strong back and very good instruction and all that equipment! And lots of practice. Enjoy!