This hat is based on my favourite object from the Portable Antiquities Scheme database: NCL-A38DF3
A Roman Millefiori glass mount http://finds.org.uk/database/artefacts/record/id/458205

GAUGE: 36 sts and 36 rows = 4” using larger needles in Fair Isle patt.
NEEDLES: 1 - 16” 2.75 mm circs and set dpns and1 - 16” 2 mm circs.
NOTIONS: Tapestry needle, 8 stitch markers,
SIZE: 19” brim circ, un-stretched, 11“diameter at widest point.
NECESSARY SKILLS: Fair Isle from charts.