And history repeats

The "Mark II" "microbombs" had Casio digital watches as the timers, stabilizers that looked like cotton wool balls, and an undetectable nitroglycerin as the explosive. Other ingredients included glycerin, nitrate, sulfuric acid, and minute concentrations of nitrobenzene, silver azide (silver trinitride), and liquid acetone. Two 9-volt batteries in each bomb were used as a power source. The batteries would be connected to light bulb filaments that would detonate the bomb. Murad and Yousef wired an SCR as the switch to trigger the filaments to detonate the bomb. There was an external socket hidden when the wires were pushed under the watch base as the bomber would wear it. The alteration was so small that the watch could still be worn in a normal manner. ^{[1] [5] [7]}

Yousef got batteries past airport security during his December 11 test bombing of Philippine Airlines Flight 434 by hiding them in hollowed-out heels of his shoes. Yousef smuggled the nitroglycerin on board by putting it inside a contact lens solution bottle.

The density of the explosive cocktail would be about 1.3.

From here. Which is talking about a 1995 bombing plot.