Also requires 4 buttons.

This pattern originally called for Biglia yarn by Adriafil, wound double. Biglia has been discontinued, and was never listed on Ravelry, but appears to have been a 100% cotton yarn of light fingering or lace weight:

Biglia
100% cotton
50 grams/ 1.76oz
200m/ 218 yards
Gauge: 34 stitches, 45 rows to make a 10cm square on size 2.5mm needles

I was unable to find a match for Biglia. As such, the other yarns suggested are substitutes for the doubled Biglia, based on gauge and put-up. They have not been tested. Make sure to swatch and proceed with caution!