Article (newsletter)  (Aug 2013)  Page(s) 5.  
 
Peter Henderson also introduced a number of roses, mostly sports of those growing in his nursery. Of at least seven roses, four are still in commerce today. ‘American Banner’ and ‘Snowball’, both sports, have disappeared, as has his hybridized rose ‘Dinsmore’, 1888.

Book  (1922)  Page(s) 187.  
 
Official List of Roses Introduced in America. Compiled by Charles E. F. Gersdorff
Snowball, Polyantha. † (P. Henderson & Co., 1899)

*varieties no longer in commerce are marked with †

Website/Catalog  (1911)  Page(s) 30.  
 
Dwarf Polyantha. Snowball. Pure white; flowers in clusters; good.

Website/Catalog  (1909)  Page(s) 89.  
 
Snowball  P.  The best white Polyantha, flowers in clusters of 25 to 50 blossoms as white as snow. 

Website/Catalog  (1903)  Page(s) 7.  
 
Monthly, or Bedding Roses
Snowball. Pure white, very neat little flower; very compact grower and very free flowering.

Website/Catalog  (1899)  Page(s) 125.  Includes photo(s).
 
Novelties among Roses are always acceptable, and in "Snowball" we have one of the most charming acquisitions imaginable, of a dwarf, compact habit, with rich, green foliage, and a bounteous blooming quality which is really wonderful. Twenty-five to fifty blossoms, white as snow and resembling a Camellia in compactness and purity of color, are produced in large clusters, literally covering the plant, its abundance of flowers, vigorous constitution, and attractive fragrance give it advantages beyond all others in this section of Roses.