From the pattern:

SIZE
One

FINISHED MEASUREMENTS
59” (long edge) x 29” (spine), sides are 42”. Size is approximate and not crucial.

MATERIALS
Koigu KPM, (100% Merino Wool; 50gr/175yds/160m per skein), 4 skeins

(1) 3mm (3US) needle, 29” or longer

GAUGE
28 sts = 10cm/4”
Gauge is not crucial.

Pattern was available here, but the link is no longer working.