Vainly awaiting the good fortune to be buried there.

Perhaps the first two lines are about Louis XVIII. He skillfully confronted the reactionaries and supported a certain level of liberalism. During his reign there was a constitutional monarchy in the country. He reformed the army, lowered the level of censorship. In 1818 the armies of the 4-sided coalition left the territory of France. The period of his reign was relatively prosperous for France.

Presumably, the last 2 lines refer to the period of the French Revolution. The monarchists wanted to organize a counter-revolution in the province of Vendee in 1793. Jean-Baptiste Carrier, a member of the Convention and Western army commissar was sent to Nantes to suppress it. He was a supporter of savage reprisals for the royalists. Instead of mass executions Carrier organized drowning of people in the Loire delta. People were put on ships with damaged bottoms and sent to the last voyage. In the future, Carrier was executed.

Linkage with other quatrains: 10.22.

Probable decoding of number 4.20. 400-20=380, 380-1=379. If 3 is put at the end then we will get 793 – the year of executions.

Quatrain 3.46 Plancus' city

Le Ciel (de Plancus la cite) nous presage

Par clairs insignes & par estoilles fixes,

Que de son change subit s'approche l'aage

Ne pour son bien ne pour les malefices.

The sky (of Plancus' city) forebodes to us

Through clear signs and fixed stars,

That the age of its sudden change is approaching,

Neither for its good, nor for its evils.