"Fred is a good mule," the wrangler drawled. "He is reliable. But he has a habit of walking close to the edge."

As I digested that, the wrangler told me how a relative would hunt game from astride a big mule, steadying the barrel of his rifle atop the mule's skull, resting between its ears. When he squeezed off a shot, the mule did not flinch. He was deaf.

The story, true or not, seemed aimed at persuading me that mules are, above all, steady and dependable and safe.

But all I could think was: Why me? Of all the mules in all the canyons in all the world, I get the one that likes to hug the edge.

What brought me to this corral full of snorting mules and champing-at-the-bit riders was a long-standing desire to see the canyon from its North Rim, which, because of remoteness, limited lodging and winter closure, gets far fewer visitors than the South Rim. Last year, more than 3 million people visited the South Rim, 10 times the total at the North Rim, which is about 10 miles away as the condor flies but more than 200 miles away by road.

At the North Rim, I also could fulfill another old goal - riding into the canyon on muleback.

The mule rides from the South Rim are notoriously popular, usually requiring reservations six months or more in advance. North Rim rides, on the other hand, can sometimes be booked the day before. Last year, 5,241 visitors took full-day mule trips at the South Rim, compared with just 623 full-day rides taken from the North Rim, the National Park Service reports.

As on the South Rim, several types of rides are available; I booked the full-day tour, which cost $125 and included a sack lunch, eaten near Roaring Springs, three hours and more than 3,000 feet down the North Kaibab Trail.

Soon enough that early August morning, I was clomping out of the corral with eight other riders, led by our wrangler, Tom Boyles. Ahead of me were two seasoned riders, Emily and Jeff - they rode mules back home in Virginia - and behind me was a family from Omaha, Bruce and Peg Larsen and their children, Abby, Sarah, Sally and Ryan. The Larsens said they had no riding experience.

The mules offered a steady ride and seemed as sure-footed as advertised. Still, they had their quirks, our wrangler warned, such as spooking when a hat blew off or when someone screamed. Mules are the hybrid offspring of a male donkey and a female horse, and they're sterile, but male or female as reflected in their names: Ben, Big Mac, Miss Piggy, Dolly.

At 8,000 feet, the air was still cool as we rode onto a gently sloping path scented with Ponderosa pine, aspen and Douglas fir. Within minutes, the trail steepened, and we leaned back in the saddles, stiffening legs against the stirrups for stability.

Three-quarters of a mile into the ride, we broke out of the pines and reached Coconino Overlook, the canyon ahead of us packed with chasms, sandstone cliff faces striated with color, and slopes peppered with piñons, junipers and scruffy vegetation.

About an hour down, we reached Supai Tunnel, a short channel chiseled through red rock that marks the limit of half-day mule rides. It's also the spot where those who want to back out of the all-day trip can turn around.

Passing through the tunnel was like going through Alice's rabbit hole. The scenery got more dramatic, the trail steeper. The vista enveloped us. Geology was within arm's reach, with each descending mule-step we now took a little jolt. The switchbacks zigzagged so abruptly it was hard to believe the mules could maneuver their large bodies so adeptly around the tight corners.

I was buzzed by the sense of height and the stark fact that a misstep could send you tumbling hundreds of feet down a jagged, prickly slope. You had to make peace with the clammy realization that you were at the mercy of your mule's judgment.

Not all the trail was harrowing - routine often settled in - but some surprise was always ahead. As we approached a blind corner, wrangler Tom told us the next stretch would be along a 1,000-foot drop-off. If we felt shaky, we should focus on the rump of the mule ahead.

It was on this stretch that Fred's daredevil edge-walking drove me to distraction. The cliffside trail was narrow, but roomy enough when the mule stayed in the middle. The chasm spooked me, and at times Fred was so close to the edge that my left knee dangled above the drop-off. So I concentrated on the mule ahead.

I had a small camera looped around a wrist and managed to shoot three minutes of video. In it, Fred's lurching to the left is obvious, and several friends later told me they could not bear to watch.

Not long after, Tom brought us to another halt.