Black Ships

The surprise and fear inspired by the first visit of the Black Ships ("kurofune") are described in this famous kyōka (a humorous poem in 31-syllable waka form):

泰平の
眠りを覚ます
上喜撰
たった四杯で
夜も眠れず

This poem is a complex set of puns (in Japanese, kakekotoba or "pivot words"). Taihei (泰平) means "tranquil"; Jōkisen (上喜撰) is the name of a costly brand of green tea containing large amounts of caffeine; and shihai (四杯) means "four cups", so a literal translation of the poem is:

Awoken from sleep
of a peaceful quiet world
by Jokisen tea;
with only four cups of it
one can't sleep even at night.

There is an alternative translation, based on the pivot words. Taihei can refer to the "Pacific Ocean" (太平); jōkisen also means "steam-powered ships" (蒸気船); and shihai also means "four vessels". The poem, therefore, has a hidden meaning:

The steam-powered ships
break the halcyon slumber
of the Pacific;
a mere four boats are enough
to make us lose sleep at night.

-- Black Ships - Wikipedia