How can I safely go downhill on an antique penny-farthing bike?

I have seen one with a mechanical brake. It consists of a lever not unlike modern levers connected to a rubber lined metal block that rubbed on the front tire near the top of the fork via linkage. No cables were used. Finding one might be quite a task. That being said, some of the reproductions use modern caliper brakes. They seem to have quite a following on the internet. Not knowing your location you might want to check for clubs in your local area.

Yeah, I suspect that nothing better than the spoon brake was ever put on those things because hard braking would send you head-over very quickly/easily.

I recall about 30 years ago reading a story of an American cyclist who went cycling in China. When he rode with a Chinese cycling club they walked up and down all non-trivial hills. Walked up because the bikes were single speed, and walked down because their brakes were so crummy.

OTOH, there was a guy in the Boston area back about 1890 who rode a century a day for a year. On a penny-farthing. I would imagine that eventually you learn some techniques.

Forget trying to use the brake to slow you down. At best, the brake may shed a little speed if you're not travelling too fast, on the flat, but backward pressure on the pedals is the more effective way to lose speed (again, only really possible on the flat). The brake will be 100% ineffective once you gather momentum and head downhill. There is one hard and fast rule to follow: If you can not see the bottom of the hill, or there are obstructions further down, which will require you to slow down or stop, then don't even attempt to ride down. Dismount and push the bike downhill.

If the view forward shows the route to be clear, and you can see the bottom of the hill then it is acceptable (though not easy for a beginner) to raise your legs over the handlebars and rest them on top. This keeps your feet out of the way of the madly spinning pedals. You will not be able to spin your legs fast enough to keep up with the pedals, so don't try to - it will end with injury of some sort.

Ignore the advice about applying the brake gently to avoid going head-first over the handlebars. You will never achieve this by using the brake alone. The original spoon brakes are just not powerful enough, and certainly will not stop the wheel quickly enough to send you over the top. "Headers" as they are known, are caused by other problems, such as the front wheel suddenly stopping because it has hit an obstacle, or become lodged in soft ground.

Well, after breaking a rib on my penny farthing, I fitted a free wheeling hub from a slider kids bike (green machine) and fitted a disc brake going downhill is fun now and my feet stay on the pedals.

Basically this is simple. Firstly make sure you control your speed from the first inch going downhill. The only way to do that effectively is by pressing back on the upward stroke. If you start early enough this will not cost too much effort and it is effective. Best remove any brake you have as this is ineffective and dangerous. Also try mounting your saddle further back on the bike. This will give you better control in any circumstance. And look ahead, more so than you are used to on your regular bicycle (this goes on the flats as well). ...and most of all have fun riding!

I read on another forum that the traditional way of doing this is to tie a rock or a stick to your bike, and let it drag behind you, so that when you're going downhill the object prevents you from going too fast. With that being said, there also exist bikes with freewheel hubs like the ones here.

Well, I've just ordered my first high wheel bike, and have not ridden one yet, but in preparation I've watched hundreds of videos and read every description of riding techniques I can find.

There appear to be five techniques for slowing the bike on steeper grades. Two involve brakes: either a spoon brake fitted atop the front wheel, or caliper or disk brakes retrofitted to the bike. These both seem inherently dangerous, as the rider's center of gravity is nearly perpendicular to the front axle, and abruptly slowing the front wheel makes it likely that the rider will be propelled over the handle bars--the dreaded header.

A third involves dismounting the saddle, and standing on the mounting step on the back of the frame and using the other foot to rub against the back of the front wheel, which seems awkward to me, but again, I've no riding experience on which to judge that.

A fourth technique is to dismount the saddle, stand on the mounting step with one foot, and drag the other foot on the rear wheel, which I've seen done in several videos with good effect, and that seems a less awkward position, at least to the casual observer.

The fifth, and most common approach, is to exert back pressure on the pedals to prevent the bike from gaining speed in the first place. Obviously, if the bike has already passed a safe speed, this becomes less and less effective as the pedals will eventually spin too fast to keep one's feet on them at all.

The best technique for slowing downhill that's not too steep is to step backwards onto the step bar, as if preparing to dismount, with your right foot pressing down onto the top of the rear wheel. Forget using the front wheel altogether - it will cripple or kill you.

Although I upvoted @Jedediah 's answer as it's the most comprehensive (and correct) answer, just a few important amplifications from somebody who rides a Penny-Farthing almost daily:

Heel on Rear Wheel:

Standing on the mount peg and pressing your heel on the rear wheel is actually a fundamental skill all Penny-Farthing riders should have. Indeed, on a Penny-Farthing without a spoon or caliper brake- my UDC 50" MK3 Penny-Farthing is such a bike- standing on the mount peg and pressing your heel on the rear-wheel is the only 2nd braking mechanism for the rear wheel. And this form of braking would ideally be applied at the top of the hill to moderate your speed.

I was riding my 50" Penny-Farthing with a group a few months ago and one rider actually lost a pedal going down a steep hill, so negative resistance on the pedals as a means of braking was not an option here. The rider resolved the issue by aiming for the biggest bush he could find- crashing- so not ideal. I suspect the rider probably put the pedals on backwards after transporting the bike to the meeting point, but in any event, being able to brake using your heel on the back wheel is your ace in a hole ;-).

Rear Wheel Caliper Brake:

I also have a UDC MK4 Penny-Farthing which ships with a mechanical rear wheel caliper brake. It is an effective braking mechanism, however possibly too effective: apply it too hard and the back wheel can walk out on you when it starts to bite. When using a rear wheel caliper brake use gradual, gentle pressure. But that is true of all braking I guess.

Negative Pressure on Pedals:

If using this method, you MUST start at the very top of the hill. If you either take your feet off the pedals, or the pedals are turning too quickly, you are a passenger at that point ;-). You'd need to brake using a rear wheel brake- either a caliper, spoon or your heel once the pedals start turning too fast.

Anyhoo, just some practical considerations on braking I've observed which might keep other Penny-Farthing riders safe

NOTE: For legal requirements concerning Brakes on a Penny-Farthing, go HERE and skip to the BRAKES section