For a hard day's night, try one of these

Shakespeare could never fathom that a Korean furniture maker in the 21st century would name his product a "Mac Bed." Nor could the French philosopher Rousseau have contemplated a "Russo" bed.

All the more, beds with special sobriquets are not your typical, comforting, fluffy furnishings. It may take a while to grow accustomed to "Mac Beds" for they use rocks like jade and granite as mattress stuffing.

Following the general belief that good names bring good luck in business, the manufacturers christened the bed Jangsoo Dolchimdae, meaning Stone Bed for Longevity. Among Koreans, the word "longevity" works like magic to enhance salability. It's no wonder that Stone Bed for Longevity's makers boasted 27 billion won ($23 million) in sales last year.

Kim Kyung-hee, a deputy manager of sales, says an explanation lies behind every bed's name. "We named each product after its designed image －－ Mac Bed for its mysterious and dark image and Russo for its solemn and dignifying image," he says.

Mr. Kim says that stone beds have heating systems, which his company invented years ago. On top of the stone or jade mattress, separated by a 2-centimeter gap, heat-generating metals like nickel warm up the mattress. The radiant heat from the generator emits infrared rays, which are beneficial to humans, according to Mr. Kim.

"It is medically proven that the infrared rays from stone beds improve blood circulation and relieve pain," he says. But he quickly adds that to a large extent, stone beds depend on an unfounded belief among Koreans that jade or certain other stones enhance one's health.

Stone beds and jade mattresses have been a can't-go-wrong gift to show filial duty to parents since being introduced in 1990. At the outset, the beds' best price of 4 million won was only available to older folks with cash to spare. Nowadays, the most affordable stone bed costs 1.7 million won, while the costliest one, containing a rare type of jade from Haeju, North Korea, sells for a cool 9 million won.

Jang Sang-woo, a Seoul officer worker, is one satisfied user of the stone bed. "It gives me a massage-like feeling," he says.

But not everyone is thrilled with the jade mattress. Choi Jeong-hee, who bought Mac Bed for her husband to soothe his lower back pain, recently came close to catching on fire.

"I smelled something burning while asleep and was astounded to find my mattress literally on fire," she says. The company said she should have used a different electric cord, but Ms. Choi is thinking of getting a refund. More typically, customers complain of body aches after their first night on the rocks. Mr. Kim at the company terms this an "adaptation period." He says, "It's like when you first start to work out. The body aches for a few weeks, but it passes."

Despite the purported risks and reported pain, Mr. Kim brims with confidence about this year's sales. "These days, the younger generations would like to try stone beds, and that guarantees our growth potential," he says. Parents buy Russo beds for their teenage kids and even newlyweds like to have Mac Beds, he added.

by Chun Su-jin