Huo Zhuan (火磚)

Drawing of a Huo Zhuan and its content, from 'Wu Bei Zhi (《武備志》)'.

Huo Zhuan (火磚, lit. 'Fire brick') was a type of brick-shaped hand grenade used by the Ming navy. It was a small box made of thin wooden plantes and filled with one jin and four liang of gunpowder charge, twenty paper firecrackers, twenty Fei Yan (飛燕) and thirty iron caltrops. The grenade was waterproofed by wrapping it in four to five layers of oil paper, and was ignited by means of a burning fuse.
Huo Zhuan measured one chi by four chun by two chun, roughly comparable in size to a large TV remote controller. It was one of the more common Ming Chinese hand grenades. Like all early grenades, there's a risk that enemy combatant would pick up the grenade and throw it back.

Variants

Huo Zhuan with three rows of Di Shu: cutaway view (above) and top view (below), from 'Wu Bei Zhi (《武備志》)'.

Huo Zhuan was such a simple weapon that many variants existed. This particular example was made of thick, oil-coated paper instead of wooden plates, and replaced its content with three rows of Di Shu (地鼠), fixed in place by bamboo strips.

Huo Zhuan with two rows of Di Shu, from 'Wu Bei Zhi (《武備志》)'.

This example contained only two rows of Di Shu and paper firecrackers. It also replaced some of its normal explosive charge with poison smoke and incendiary gunpowder, and featured a fuse protector made of bamboo tube.