Definitely possible if its cubensis, but its not something you see every day
Look at some of the pictures in this thread:
http://www.psychedelia.dk/phpBB3/viewtopic.php?f=2&t=10420&start=20
Its not in english I know, but dont mind the text
i myself have came across many a large varieties. the heaviest being amazonian a.k.a. "Penis Envy"
A dried mushroom weighing 3.5g? Doesn't sound likely.