 Shares of Casper Sleep Inc. surged 4.8 toward a three-month high in premarket trading Thursday, after the mattress-in-a-box seller reported a narrower loss and revenue that rose above expectation, and provided an upbeat outlook. The net loss narrowed to 21.2 million, or 52 cents a share, from 34.0 million, or 1.23 a share, in the year-ago period. 