devtools::load_all()
 NLD_prov$x = seq(10, by = 5, length.out = 12)
 
	tm_shape(NLD_prov) + 
	 	tm_symbols(size = "x", size.scale = tm_scale_continuous(values.scale = 4)) + 
		tm_text(
			text = "x"
		)
#> Erreur : Incorrect values for layer text, aesthetic text; values should conform visual variable "text".