Leaflet for non-geographic data (Cartesian coordinates) from R

I am trying to create an interactive plot with a flyer containing polygons. The coordinates of these polygons are not longitude / latitudes, but rather the Cartesian x and y coordinates that represent the floor plan of the building.

For coordinates that are single digits, the results look good:

library(leaflet)
library(sp)
Sr1 = Polygon(cbind(c(9, 8, 8, 9, 9), 
                    c(3, 3, 4, 4, 3)))

Srs1 = Polygons(list(Sr1), "s1")
SpP = SpatialPolygons(list(Srs1), 1L)
leaflet() %>% addPolygons(data = SpP)

      

        
        
        
      

    

But when I increase all y-coordinates by 100, things go wrong:

library(leaflet)
library(sp)
Sr1 = Polygon(cbind(c(9, 8, 8, 9, 9), 
                    c(103, 103, 104, 104, 103)))

Srs1 = Polygons(list(Sr1), "s1")
SpP = SpatialPolygons(list(Srs1), 1L)
leaflet() %>% addPolygons(data = SpP)

      

        
        
        
      

    

I am assuming this is due to the default projection settings on the map. I tried to initialize the map with these settings:

leaflet(options(crsClass = "L.CRS.Simple"))

      

        
        
        
      

    

After reading this example, but no success.