Nightcaps are no longer part of a standard wardrobe, but their construction is very simple. A triangular piece of fabric is sewn together and worn on the head for warmth during sleep. This is the sort of cap mentioned in the famous poem "'Twas the Night Before Christmas," by Henry Livingston, and seen in visual depictions of Scrooge meeting ghosts in "A Christmas Carol," by Charles Dickens. Today, nightcaps are old-fashioned solutions to unheated houses.
Measure around the circumference of your head with measuring tape and mark this distance in chalk on the wrong side of your flannel, adding an extra inch to each end. This length, plus an inch of seam allowance, will be the width of one side of your cap.
From the middle of your chalk line, draw a second line of about 18 to 20 inches straight up. This is the length of the decorative point on your cap.
Complete the triangle shape by joining the top of the 18 to 20 inch line with the ends of the line that is the circumference of your head.
Following the chalk lines, cut out the triangle shape with scissors and fold in half, wrong-side out. Your fold line will be the 18 to 20 inch chalk line.
Sew along the side of the folded triangle and hem the circumference line. Your extra inch of seam allowance at each end of this line will give you a loose, comfortable fit.
Turn right side out, and use needle and thread to secure the tassel to the tip of the finished cap.
A silk lining may be added to help protect your hair from damage. Fleece is a warm alternative material to flannel, but will not be historically accurate.
Take care when using sharp scissors and needles to avoid injury.