The Incompleat Enchanter & The Castle of Iron by L. Sprague de Camp & Pratt 1968
The Incompleat Enchanter
The Mathematics of Magic—it was the greatest discovery ever. Or so thought Professor Harold Shea. With the proper equations he could instantly transport himself and his friend Reed Chalmers back—or sideways—in time to all the wondrous lands of ancient myth and legend.
But slips in time were a hazard. and Shea's magic didn't always work quite as he expected. A dragon spell might yield a hundred dragons—or, even worse, one-tenth of a dragon. And the various imaginary lands he travelled to held countless dangers that even Shea's equations couldn't predict...
The Castle of Iron
The Mathematics of Magic—it was the greatest discovery ever. Or so thought Professor Harold Shea. With the proper equations, he could instantly transport himself and his long-suffering colleagues back—or sideways—in time to all the wondrous lands of ancient myth and legend.
But slips in time were a hazard, and Shea's magic sometimes backfired. When it did, the results were usually bizarre at best—and potentially lethal at worst. The imaginary lands to which Shea travelled held countless real dangers that even the magic equations couldn't predict.
