Mirabiliary is an obsolete word that appeared, and then left again, in the early 1600s. It is simply a miracle-monger, although it is more realistically defined one who deals in the marvelous or a collector of marvels.
It comes from the Latin mīrābiliārius, which was used to refer to things supernatural, although in latter ecclesiastical Latin it took on the meaning of a worker of miracles or wonder-worker.
Those things that a mirabiliary collects and/or does are mirabilia.