Iridehorses, you took the words out of my fingertips! I too recommend picking a day when it won't rain, grab a book and some snacks (preferably granola bars in really loud, crinkly wrappers) and just hang out in his pasture. I'm sure your curious horse will come check you out eventually. When he comes up to you, don't grab him right away. If he comes really close, maybe give him a pet (or a bite of your granola bar).
You may have to invite/allow him into your space for many days before he is comfortable sharing a bubble with you. Just be calm and consistent, and soon enough, you'll be pushing him OUT of your space whenever you try to eat a granola bar!! :)