What was the time machine originally supposed to be in Bill & Ted’s Excellent Adventure?

What was the time machine originally supposed to be in Bill & Ted’s Excellent Adventure?
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Put “Be excellent to each other” on my gravestone. Tattoo it on my chest. Etch it into every tree you see.

It’s hard to imagine pitching an idea for a movie much wackier than Bill & Ted’s Excellent Adventure, in which two wannabe rockstar teenagers — William "Bill" S. Preston, Esq., and Ted "Theodore" Logan — must travel back in time to collect historical figures in order to pass their final exam — because if they don’t, they will never turn Wyld Stallyns into the biggest rock band of all time and bring peace to the world. 

Yet the 1989 film was highly profitable and launched Keanu Reeves into becoming one of the biggest stars on the planet. Most triumphant!

Oh yeah, and they use a phone booth to time travel, dialing numbers out of some kind of future phone book (good to know they still have those in the year 2688) that take them to important moments in world history. And let’s be honest, Socrates is the only one who reacts appropriately when he meets people from the future and is taken on an adventure through time.

Like sands through the hourglass. . . - GIFs - Imgur

But the iconic phone booth was originally going to be something else. What was the time machine originally supposed to be in Bill & Ted’s Excellent Adventure?

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