A water clock was an excellent idea -- she'd kept on thinking of more natural phenomenon, until he and Nina had started going back and forth about translation and clocks, and it wasn't cherry blossom petals or dead leaves, even if they tended to fall with edges cupped upwards. Lots of things could act like a clock -- accidental homicide via ice carving was the least weird of the cases that sprung to mind.

But a trip down memory lane wasn't going to stop their five minutes from running--hold it!. Running out on them. Of course.

"That's it! It's an egg timer." About the same amount of time as they'd been given, really, and she narrowed her eyes at the Sphinx. Had that been a hint? Not the time, but the reminder that it was halfway up. "Or, more generally speaking, an hourglass."

She thought a moment, and then added. "Or would the answer properly be the grains of sand themselves?" A technicality, to be sure, but the Sphinx's anticipation of their failure had looked disturbingly reminiscent of von Karma's sharklike grin. Except with teeth that could actually back it up.