Drawing, [calculations of supporting surfaces for full size rigid stable aeroplane], Lawrence Hargrave, Sydney, New South Wales, Australia, 
Red ink on paper. With pencil annotations by Hargrave. Dated at upper left 'Feb 1910'. Calculations are on the reverse of two circulars pasted together - one being an Aerial League of Australia circular, 20 January 1910, the other an Engineering Assocation of NSW circular, 17 January 1910.
Pencil annotation by W. Hudson Shaw at lower right reads: 'Calculation of supporting surface/required for RSA (full size)'.