How to project to oblique Mollweide

Question

I know how to produce a map with the Mollweide projection, both using QGIS and R (I'm most interested in doing all of this in R). The proj4string that I've used in R is +proj=moll +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs

But I am interested in producing a map using what I've seen called the Mollweide oblique projection, or the Atlantis projection, or alternatively the "Hammer map". See here for examples.

I'm not quite sure where to start, though.

Does this involve adjusting some of the parameters in the above Mollweide proj4string?

For starters, here is how I get a map in Mollweide projection:

library(maptools)
data(wrld_simpl)

mollCRS <- CRS('+proj=moll +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs')

mollMap <- spTransform(wrld_simpl, mollCRS)