Pyrotechnic Weapons -- Naft Zarraga

The above conjectural drawing is a reconstruction of a portable Greek Fire
siphon from a number of written descriptions plus highly stylized
illustrations in Byzantine and Islamic military manuals.  An airtight
 copper "box" (tank) containing inflammable liquid is mounted
above a hand-held siphon.

Reference:

D. Nicolle, et al, "Medieval Siege Weapons (2)," New Vanguard 69, Osprey, Oxford, UK, 2003