Solo Sahara crossing in 1938.

M. Douard with his Jonghi.

Daniel André Douard, Guard of the French Republic, pictured 1 February 1938 just about to set off on a solo crossing of the Sahara on his 100cc Prester Jonghi.

Douard's crossing was successful and he wrote a book about his exploits with a Dr T Malachowski which was published in 1939 (La traversée du Sahara, seul en Vélomoteur par le Garde Républicain Douard). The book appears to be not too uncommon and copies are available on the internet from around 30 to 70 euros. Sadly there is no English language translation available. 

The route Douard took was from South to North and is claimed to be the first solo crossing using the Tanezrouft Piste route. He began the journey February 1938 in Gao, Mali, and ended in Algeria 1930 kilometers and 18 days later. Douard's expedition is also claimed to be the first solo moped crossing of the Sahara, though if you can really call a 100cc machine with three gears a moped is debatable magnificent as his feat certainly was.

He must have been roasting hot in those shiny black leathers. Note the auxiliary fuel tank mounted down by the rear wheel. 

Frontispiece of M. Douard's book of his exploits.