Diet of Porvoo
The Diet of Porvoo ( Finnish "Porvoon maapäivät" , or unhistorically "Porvoon valtiopäivät"; Swedish "Borgå lantdag"; Russian "Боргоский сейм" ) , was the summoned legislative assembly to establish the Grand Principality of Finland in 1809 and the heir of the powers of the Swedish Riksdag of the Estates . 
<triplet> Diet of Porvoo <subj> legislative assembly <obj> instance of <triplet> Grand Principality of Finland <subj> 1809 <obj> inception