Maybe I was thinking of a route with changes that I had seen. It is possible to get from Paris to Le Puy on the same day, via either St Etienne Chateaucreux, or Brioude. I got these times from the SNCF site:
PARIS GARE DE LYON 07h00 TGV DUPLEX 6681 Peak period
ST ETIENNE CHATEAUCREUX 09h41 Disabled Buffet car
ST ETIENNE CHATEAUCREUX 09h57 TER 89966
LE PUY EN VELAY 11h17 Carriage of bicycle
Departure and destination stations Times Train(s) Journey time: 06h20
PARIS GARE DE LYON 08h47 CORAIL 5957
BRIOUDE 13h51 Disabled Family compartment Trolley service
BRIOUDE 14h00 Coach 31343
LE PUY EN VELAY 15h07
Departure and destination stations Times Train(s) Journey time: 04h17
PARIS GARE DE LYON 13h00 TGV DUPLEX 6685 Off peak
ST ETIENNE CHATEAUCREUX 15h47 Disabled Buffet car
ST ETIENNE CHATEAUCREUX 15h57 TER 89974
LE PUY EN VELAY 17h17 Carriage of bicycle