One verse

Srimad Bhagavatam 4.8.56

4.8.56

लब्ध्वा द्रव्यमयीमर्चां क्षित्यम्ब्वादिषु वार्चयेत् । आभृतात्मा मुनि: शान्तो यतवाङ्‌मितवन्यभुक् ॥ ५६ ॥

labdhva dravyamayim arcam ksity-ambv-adisu varcayet abhrtatma munih santo yata-van mita-vanya-bhuk

labdhva
by getting
dravya-mayim
made of physical elements
arcam
worshipable Deity
ksiti
earth
ambu
water
adisu
beginning with
va
or
arcayet
worship
abhrta-atma
one who is fully self-controlled
munih
a great personality
santah
peacefully
yata-vak
controlling the force of talking
mita
frugal
vanya-bhuk
eating whatever is available in the forest.

It is possible to worship a form of the Lord made of physical elements such as earth, water, pulp, wood and metal. In the forest one can make a form with no more than earth and water and worship Him according to the above principles. A devotee who has full control over his self should be very sober and peaceful and must be satisfied simply with eating whatever fruits and vegetables are available in the forest.