Example in the book

# modern way to do this conversion (but currently looses the CRS attribute):
map_4326 |> 
  st_geometry() |> 
  st_transform("EPSG:5356") |> 
  st_transform(pipeline = "+proj=unitconvert +xy_out=km")

## Geometry set for 1 feature 
## Geometry type: MULTIPOLYGON
## Dimension:     XY
## Bounding box:  xmin: 431.3593 ymin: 7467.767 xmax: 1723.061 ymax: 8924.548
## CRS:           NA

## MULTIPOLYGON (((445.7616 8064.389, 445.7457 806...