The old nostrum "pack it in, pack it out" takes on a new dimension when one member of your backcountry party happens to wear Pampers--and hasn't yet learned to crawl, much less carry his own pack.

About this time last summer, my wife and I arrived at a trailhead in the Mount Jefferson Wilderness, just outside of Camp Sherman, and shouldered our respective burdens. Hers consisted of 18 pounds of boy, strapped into what appeared to be a James Bond jetpack, a brand new Kelty Explorer, the La-Z Boy of baby carriers. The Explorer comes with a nylon sun canopy, stirrups on bungees for two bouncy little feet and a 1-liter water reservoir with a sip tube for the wearer. Tucked below the padded seat, there's a toxic-waste storage compartment that Kelty, in its infinite wisdom, designates as the "Poop Deck."

This meant I carried everything else: three sleeping bags, three air mattresses, one tent, a stove, an Outback Oven (if you don't have one, you should), food, three days' worth of diapers, clothes, water purifier, mess kit, and pots and pans. Imagine Jed Clampett in Danner boots.

After the first 15 steps of an intended 18-mile loop, I was ready to sit down. Not just because of the damned anvil on my back, but because of the music: gurgling water mixed with the staccato sounds of hovering rufous hummingbirds; the strange songs of MacGillivray's warblers, pudgy little green birds with blue heads; plus one little boy flapping his arms and yipping with delight. As the trail continued along Candle Creek, we stopped again. This time the excuse was the largest California white fir in Oregon, a tree so large that four adults together couldn't hug it if they tried.

Then, suddenly, we were standing at the edge of an immobile river of rock, a recent (7,000-year-old) lava flow that stretches along the bottom of a deep glacial canyon, up to a dormant cinder cone on the southernmost flanks of Mount Jefferson. We picked our way over ankle-breaking basaltic andesite skree and re-entered the forest. For the next five hours, with lava on our right and impenetrable forest on our left, we staggered up the trail, helping each other over and under fallen logs. Finally, we pitched our tent on an exposed shelf of rock overlooking the cinder cone, miles short of our intended camp. After an energy bar dinner, we went to sleep.

We woke to a malevolent wind. And endless rain. In Portland, it had been 95 degrees, hadn't rained in weeks. We hadn't packed any Gore-Tex. Or thermal underwear. Besides, with the diapers, there simply wasn't room. So we stayed put, alternately playing, eating (coffee cake, focaccia, lasagna and pizza) and sleeping until two days later, with a happy boy and a Poop Deck that reeked like roadkill, we returned the way we came.

We haven't been hiking since.

To reach the Jefferson Lake trailhead, head northwest from Sisters on Highway 20; then turn north on Forest Service Road 12. Follow FS Road 12 for 12.1 miles; then head north on FS Road 1290 for 0.4 miles. Take FS Road 1292 west for 2.4 miles to the trailhead. The reviled Northwest Forest Pass ($5 per day) is required.

The 18-mile Jefferson Lake loop is made up of three trails: Jefferson Lake Trail (Trail No. 4001), Cabot Lake Trail (No. 4003) and the Sugar Pine Ridge Trail (No. 4002). For more information, call the Sisters Ranger Station at (541) 549-7700. Maps and complete trail descriptions are available on the Forest Service website ( www.fs.fed.us/r6/centraloregon/recinfo/trails/summer/54001_0.html ).

If you've never heard of the Outback Oven (or if you want to know where to get one) check out www.backpackerspantry.com .