The mobile toilet. Long an object of fascination for me. I don't mean the glass pottie with the little decal of a toy soldier in red that we carried with us in the car. If one of us had to pee, we'd pull over, take it out from under the front seat, place it on the ground and—shielded between the open car doors and someone standing guard—pee. Our level of anxiety during this operation would correspond to the amount and speed of traffic passing by. Or our place in line.

Before either of my sisters beats me to it, I'll raise the question of memory. After Ann and I strongly disagreed about whose socks Jeanie accidently peed on in Denver (poor little Jeanie—too much traffic to stop), we had to laugh despite our equally vivid victim memories. We agreed that we should pick a few famous family incidents and each write our version. But Jeanie's too busy making quilts and working at the Montessori school, Ann too busy writing her encyclopedia of women composers and lyricists, and Frank too busy with his family, nevermind running all over New Mexico as an opthalmologist. What worries me is that little soldier on the pottie. I expect to hear from one of them saying he didn't exist. But I feel so certain about it because every time it was my turn, I would sit there and think about how odd it was that the soldier was there. Like a little friend, smiling. Hello again, I'm here with you.

I don't remember which came first: the narrow gauge train ride from Durango to Silverton, Colorado, or the Trailways bus ride from Tulsa to visit our grandparents in Orlando, Oklahoma. But Jeanie was my companion in discovering the delights of peeing in certain moving vehicles, somewhere in the middle of the 20th century. The delight came from feeling the caress of a light whirlwind as we sat swaying with the movement of bus or train. We solved the mystery of this phenomenon by looking down into the toilet, where we saw highway or train tracks passing in a blur. I couldn't say how many times we jumped up and made our way to the cubicle at the rear of the bus. We were riding alone; I was the oldest. On the train, we must have left the rest of the family behind more than once to experience again and again the joy of this secret—and simple—pleasure.

A friend on Martha's Vineyard has an ingenious and creative husband. He installed a marine toilet in her little cottage there. Which means that instead of a porcelain slope and gallons of water, there is a chute. I think he also installed some kind of air pump so that everything goes neatly down with a whoosh, with a hose nearby if needed.

The motorhome has a similar arrangement. No, you can't see the highway. No, there's no wind. And yes, there are holding tanks, that's later. But what you rapidly get used to is the convenience of awkwardly walking to the back while in motion, and then the immediate relief. Any gracefully aging older woman knows the joy in this arrangement—as does her traveling partner, who may or may not have as frequent urges. Add to that the rush of adrenalin as you sit rocked by passing semis, or lurching in rush hour traffic in St. Louis. I'll let you imagine what it's like to stand and get your pants back up.

At first, it's strange without the water. After a while, it feels natural, if not downright virtuous. At the base of the toilet, step on the pedal to the left. A door magically opens, a small amount of water swooshes everything down in an instant, and with the release of the pedal, the door snaps shut. If more water is needed, there's the pedal on the right.

The unpleasant part is of course dumping the holding tank. Or the sudden aural sense that it needs dumped—badly—with no opportunity present. In Alberta, BC and other parts of Canada, free dump stations are kindly furnished. At the RV parks, it's included with a full hook-up of electricity, water, sometimes cable, sometimes wi-fi. Whenever I think of all the RVs I see on the road dumping, I get a feeling similar to thinking about all the pencils or straws being made at one moment in the world. Too too much. How can our earth sustain us all? Oops, I'll rush back to the specific: after the dumping, there's the charging. Putting in the current environmentally safe chemicals, purple in our case, and then adding a few gallons of water. Voila, until the next time.

One of my big adjustments when I get home: all that water. The splashing. The slow—and sometimes inefficient, insufficient—gurgling down. For now, that's in my not-so-distant future. So I'll just continue with what I've been trying to learn to do for years: enjoy the moment. We just dumped. We're in Dawson Creek, BC, with an empty tank and a full day to explore here.