I'm a M.Sc student in europe who is collaborating with a prof on a research project. He works in an institute which is in a different city than mine. He has offered to cover my up and down weekely train tickets.
Though the train trip in one direction is just 3 hours. Its during the lunch and dinner times when I'm on the train and the meals on the train are not included on the ticket and quite expensive for a weekly affair. For now, I pack some snacks with me but its by no means a full satisfactory meal. Essentially I starve for the whole day with no eating options at the host institute. Moreover, I travel for 45 mins by public transport one way from the station to the institute (i'm not sure if I can ask for taxi expenses either)
The meetings are for discussions on progress, ideas and general presentations on relevant papers. Its been very useful but I don't want to extend his generosity beyond the point where it becomes unprofessional.
I wish to keep this collaboration between me and him as professional as possible. Since I have no prior experience of a professor inviting me for discussing and working towards a common goal, I fail to find the line between ethical and unethical expenses which I can ask the supervisor for.
Any suggestions are appreciated! Thanks