Suggestions for type of beams?

[Traveller]

Hi all.

Similar to the illustration in this link and ignoring the type of end posts, if there were two parallel beams set apart about 20cm (so there is a gap between them) and were about 110cm long and the load was about 75kg, could anyone suggest what type and dimensions of beams would be needed to comfortably bear this load (the cheapest, lightest option)? The beams don't need to be flat like in the illustration, it would be ok if they are more 'square' in shape, or maybe even preferrable as the more surface area, the better.

Thanks for any advice.

 

[Dereekoo]

16 x 90 plank of c16 wood or 50 x 50. Based on pure strength, other things like deflection and lateral stability and FoS come into play but it gives you an idea

 

[Traveller]

Thanks.