The new remarkably soft and plush socks from the shoemaker Harrys of London are made of a rare, superfine material (13-micron diameter) known as Cervelt, which is woven from the down of New Zealand red deer. In addition to providing a soft feel, the limited-edition socks ($1,460 per pair) are especially strong and resilient and retain their warmth thanks to the natural curled shape of the fiber. Upon the discovery of the down’s thermal and wicking properties, the New Zealand company Douglas Creek spent eight y…