I missed it last year. But how interesting is this. I would also like to understand how the three filters were used with a large format. I am assuming he held a different filter (times 3) while the subject held very still, all in one continuos shot (either that or shot three different images with the different filters and then merged in darkroom)
What amazes me is how (back in 1909+) he ended up with very vivid color images. They look like they were taken recently.
Trying to decipher the poorly written write-up it appears that he did shoot three distinct exposures with RGB filters. For displaying the color photos he projected the shots using three projectors with each of them having corresponding RGB filters, not unlike a slide show (not Lightroom slideshow, a proper Velvia slideshow

). (edit:
Wikipedia confirms this, uncited as usual.) What the article doesn't mention is how they produced the postcards (which were apparently like SMSs are these days).
I'm also shocked how vivid the images look, and need to check if there's an exchibition nearby.