I've heard Hindus say that Hinduism is monotheistic (in truth it's polytheistic and pantheistic), but historically the pie religion was polytheistic.
Can anyone verify this?
Yeah, go talk to a Hindu, or read some books about Hinduism and then you'll have a better since of what Hinduism is and isn't. Hinduism really is hard to nail down. There is no set of "official teachings" or dogmas, and people are free to be devoted to one god, many gods, or no gods at all.
From my reading, it seems to be that most of Hinduism is on some level monotheistic, at least in philosophy anyways. What Christians would call "God", Hindus call The Brahman, or the One, or the first cause, or as wikipedia puts it:
the eternal, unchanging, infinite, immanent, and transcendent reality which is the Divine Ground of all matter, energy, time, space, being, and everything beyond in this Universe.Sounds sort of like some descriptions of the Christian God, albeit from the more mystical/apophatic traditions within Christianity to me. Not that there are NO differences because there certainly are. But at least on a superficial level, most Hindus accept the Brahman as the "cause" of all, and that nothing not even the "gods" exist eternally apart from the Brahman. If I'm not mistaken I believe that the "gods" are in fact manifestations of this ultimate reality, or of this ultimate Creator God (The Brahman), because these manifestations, or avatars or whatever they're called are humanities only way of comprehending the Brahman.
The many gods were once described to me by a one time Hindu as a prism reflecting the sunlight. It reflects light in hundreds maybe thousands of different ways, colors, small dots, large beams etc...but all these different reflections of light (the gods) are in fact all reflecting the very same ultimate reality/God/source of being (The Brahman). In Hinduism it's my understanding that each person chooses which color of beam to follow (using the prism analogy), some follow one, 3, 100 etc....Some Hindus have no problem accepting Jesus as one of these refractions of light coming through the prism either.
So I suppose in practice Hinduism could be considered "polytheistic", but in philosophy it's much closer to monotheism. I don't really think either definition is accurate though because Hinduism as others have said is not monolithic and there are so many schools of thought and practice that it would take 100 lifetimes to begin to understand Hinduism.

(get it, 100 lifetimes?

)