In Arabic "rubai'i" refers to a type of 4-line verse, & this is a book of them, like Omar Khayyam's
[DOC] [TLE] Thger Larsen: Bakker og Blger (1912) [19: Omar Khayym] [PAR] Medens Omar Khayym's Rubiyt i Edward Fitzgerald's Gengivelse gaar sin 
Sejrsgang ... Omar bad om at maatte leve i en Krog under hans Lykkes Skygge 
for at udbrede Videnskaben.