Personally I have little fear of spiders and as a child used to collect the biggest ones by hand from our garden and keep them in empty plastic toffee jars, the kind in which loose sweets are sold. I had some big and boldly coloured garden spiders, maybe the biggest being the size of an adult thumb, legs included. They did bite me several times, but with no effect. Other than giving me super-strength, the ability to sense danger, climb skyscrapers etc..
On arriving in Sydney for a holiday a few years ago, one of the first places I visited was the city's main museum. They had an exhibition of spiders on, and a few of the displays were interactive, in that you could explore a mock-up room and try to find the 10 different live spiders that were hidden (behind a little glass window) in it.
For example, there was a shed with a black window in a glass-topped paint can etc. It was pretty amusing watching people freak, there were even big Huntsman spiders under beds etc.
It served me well, because a few days after I visited a bush park around Sydney which had rapidly grown back after being recently decimated by forest fires. Whilst visiting the public "Dunnie" I closed the door of the stall and was faced with a Huntsman on the back of the door.
It was bigger than my adult hand, and fortunately I had my camera with me, so I took a photo of my hand next to the spider. I love the effect that picture had on people when they were absent-mindedly leafing through my Australia snaps!
Afterwards I decided to remove the spider with a folded map, in case it caused the next stall-user to have a heart attack. I carried the specimen (the spider, not my call of nature) out on the back of the map and was surprised at the screams it generated. Surely these spiders are not uncommon in such a place?
I would have loved to have seen that 4-footer though. I know things seem bigger when you are small, like Bazooka Joe bubble gum seems so small and poor value for money now. Allowing for this, I imagine that a perceived 4-footer must have at least been 12" or more at the most pessimistic estimate.
BTW, for those of whom the sight of a spider induces mortal terror (like my wife) there is a neat plug-in device which pulses an ultrasonic frequency which spiders and other insects do not like. It's about the size of one of those plug-in air-fresheners and since buying one over the internet 3 years ago, we have had very few spiders in the house. In short, it seems to work.