Seneca, Ad Lucilium Epistulae Morales, 58.31, on Plato's lifespan:
Nam hoc scis, puto, Platoni diligentiae suae beneficio contigisse, quod natali suo decessit et annum unum atque octogensimum inplevit sine ulla deductione. Ideo magi, qui forte Athenis erant, inmolaverunt defuncto, amplioris fuisse sortis quam humanae rati, quia consummasset perfectissimum numerum, quem novem novies multiplicata conponunt.
For I suppose you know that thanks to his careful management, Plato completed eighty-one years of life and died on his birthday, not a day short. For that reason, some Persian soothsayers who happened to be in Athens made burnt offerings to him after his death, believing that since he had completed the most perfect number (which they get by multiplying nine times nine), his fate was of more than humankind.
I can't understand the literal meaning of the sentence amplioris fuisse sortis quam humanae rati, especially the phrase humanae rati. Also I wonder why he used fuisse, instead of a participle.